Updated

Thousands of people may have been killed or injured Thursday in a horrific train collision and explosion at a station near the Chinese border, according to South Korean news media, just hours after North Korean President Kim Jong Il (search) had passed through the same spot.

The Red Cross (search) reported on Friday that 54 had been killed and 1,249 were injured, but they said those numbers were expected to rise as many are feared buried under rubble.

South Korean media reports said that as many as 3,000 people might have been killed or injured, while the Chinese Embassy in North Korea confirmed that two Chinese were killed and 12 others injured in the disaster, the official Xinhua news agency reported. It did not say how many North Koreans were killed.

Xinhua said the blast knocked down more than 20 houses.

The Red Cross also said the train was carrying explosives similar to those used in mining, not fuel as the initial reports stated.

The blast was so strong that debris flew into the air for 10 miles around the crash site. North Korea declared a state of emergency after the crash, but the country's secretive communist government cut international phone lines and stopped information from leaking out.

Jeong Se-hyun, in charge of Seoul's relations with communist North Korea, said China has been urging North Korea to send injured people across the border to hospitals in China, but that North Korea has instead been asking China to dispatch relief workers to the scene of the disaster.

The North's official KCNA news agency still had not mentioned the disaster by Friday morning, more than 20 hours after the blast.

South Korean President Goh Kun also ordered officials to prepare aid, his office said.

"If the reports are true it is a very unfortunate accident. We extend our deep condolences," Goh told officials in remarks confirmed by his office to Reuters. "I have asked related government offices to prepare humanitarian aid measures quickly, if necessary."

A doctor in Dandong told Reuters on Friday his hospital had been told by Chinese authorities to prepare for thousands of dead and injured.

"They told us to get prepared. They only informed us that thousands were dead or injured," the doctor at a major hospital told the news service by telephone from Dandong, about 30 miles from the site of the accident.

The Red Cross was holding an emergency meeting in the North Korean capital, Pyongyang, officials said.

"We're in meetings in Pyongyang to confirm what actually happened," a Beijing-based official for the International Federation of Red Cross and Red Crescent Societies told Reuters.

The British Broadcasting Corporation showed on its Web site what it claimed to be a black-and-white satellite photo taken 18 hours after reported explosion. The photo showed huge clouds of black smoke billowing from the alleged blast site.

A cross-border train shuttling a large number of Chinese residents was at the train station during the explosion, South Korean newspaper JoongAng Ilbo reported Friday. It did not say how many Chinese were aboard the train and estimated up to 3,000 people were killed or injured.

"A passenger train that connects China and North Korea and was carrying many Chinese living in the North was stopped at the station when the accident happened," the newspaper said.

South Korea's Defense Ministry confirmed Friday that there was an explosion at Ryongchon (search), a town 12 miles from China, but could not provide further details. "All we know is that there was a large explosion," a ministry spokesman said on condition of anonymity.

Almost immediately following the crash of the two trains, one carrying oil and the other liquefied petroleum, rumors spread that it could have been a deliberate attempt on Kim’s life.

But senior U.S. Defense Department officials told Fox News there wasn't any information to substantiate such theories and the collision was more likely a tragic accident.

A South Korean official, quoted on condition of anonymity by South Korea's all-news cable channel, YTN, said it appeared to be an accident.

U.S. State Department spokesman Richard Boucher said the Bush administration had no information on the collision.

Ryongchon has a reported population of 130,000 and is known for its chemical and metalwork plants.

South Korean news organizations reported that the collision took place about 1 p.m. Thursday. On Friday, however, YTN cited government sources as saying that the blast was triggered by a train carrying LPG and there wasn't a crash. Because of the absence of official information, there was no immediate way to clarify the discrepancy.

North Korean authorities placed a total news blackout on information about the crash, according to Chinese news reports, taking such drastic measures as cutting international phone lines in and around Ryongchon.

"The area around Ryongchon station has turned into ruins as if it were bombarded," Yonhap news agency quoted witnesses as saying. "Debris from the explosion soared high into the sky and drifted to Sinuju," a North Korean town on the border with China, the agency said.

About nine hours before the blast, Kim had reportedly passed through the station where the collision happened as he returned from a secret trip to China, YTN reported. Kim met with the country's leaders and discussed the standoff over the North's nuclear weapons program.

North Korea's state-run news agency on Thursday confirmed that Kim had made a secretive trip to China on Monday through Wednesday, but carried no comments on the reported explosion.

Many of the blast survivors were transferred back to China to receive treatment, which seemed to be how news of the catastrophe spread despite the North Korea-imposed news blackout.

Cho Sung-dae, a Yonhap correspondent in Beijing, said his reports were based on residents in the Chinese border city of Dandong who talked with their relatives in Ryongchon.

They described a massive explosion involving a large number of casualties but could not give figures, Cho told The Associated Press. Cho also said North Korean authorities appeared to shut down the border with China after the incident.

Subsequent attempts by his Chinese sources to contact people in Ryongchon failed because the phone lines apparently had been severed.

YTN and Yonhap reported that the number killed or injured could reach 3,000. Both organizations said their casualty counts came from South Korean government sources, whom they declined to further identify.

James Lilley (search), a former U.S. ambassador to South Korea and to China, said he saw a possibility that anti-Kim forces could have tried to carry out an assassination attempt like this.

"They realize the system depends so much on him and the system is so bad and punitive that some people could have just taken the situation into their own hands," he told Fox News.

Lilley said an accident of this magnitude would make it impossible for the North Koreans to keep quiet.

"I'm sure this kind of thing happens quite frequently in North Korea," Lilley said. "Their infrastructure is deteriorating fast."

Analysts differed on whether the incident was planned.

"If it was an assassination attempt, it was a poor one," John Wolfsthal of the Carnegie Endowment for International Peace (search) told Fox News. He said it was doubtful because of the nine-hour difference between when Kim passed through and when the collision and explosion occurred.

But Wolfsthal added that the brutal dictatorial Kim regime would likely use the crash to its advantage.

"The leadership may use this as an opportunity to clamp down on whatever dissent or instability there might be," he told Fox News. "We will be watching closely to see how Kim Jong Il responds."

Kim apparently had a soft spot for Ryongchon. He often visited the town and its machine-tool factory.

Chinese and North Korean traders frequently cross the border at Dandong, a bustling industrial city on Yalu River.

China, which also confirmed Kim's visit, is North Korea's last major ally, and the two countries' ruling communist parties boast of close ties. But while China's experiments with capitalism have transformed it into an economic dynamo, North Korea suffers chronic food shortages and depends on its larger neighbor for aid.

Thursday's accident resembled a disaster in Iran on Feb. 18, when runaway train cars carrying fuel and industrial chemicals derailed in the town Neyshabur, setting off explosions that destroyed five villages. At least 200 people were killed.

North Korea is one of the world's most isolated countries and rarely allows visits by outside journalists. News events within its borders are difficult to confirm independently, and the state-controlled media is unlikely to provide quick confirmation of such an accident.

The communist country's infrastructure is dilapidated and accident-prone. Its passenger cars are usually packed with people, and defectors say trains are seldom punctual and frequently break down.

Sometimes, trains are stranded for hours at stations until their electricity supply is restored enabling them to continue, some defectors say.

The trunk line on which Thursday's accident reportedly occurred, the main rail link between China and North Korea, was first laid during the Japanese occupation more than 60 years ago.

Fox News' Marie-France Han, Catherine Donaldson-Evans, Jonathan Hunt, Bret Baier, Andrew Hard and The Associated Press contributed to this report.