Updated

Rescuers searched for survivors in the ruins of a collapsed apartment Wednesday, but there was little hope of finding anyone 24 hours after a gas explosion ripped the building apart and killed at least 50 residents.

Police were searching for two homeless men suspected of triggering the deadly blast by stealing metal fittings from gas pipes to sell for scrap.

The explosion ripped through a prefabricated building in Arkhangelsk (search), a White Sea port about 600 miles north of Moscow, before dawn Tuesday, destroying an entire nine-story section and trapping dozens of people in the rubble. Twenty-four people were rescued, including two children.

On Wednesday the death toll rose to 50, including eight children, emergency and rescue officials said.

"Unfortunately, there is very little probability that people are alive under the debris," Deputy Emergency Situations Minister Yuri Vorobyov told Russia's NTV television.

Officials gave conflicting accounts, saying from nine to 20 people still were missing. There was confusion because often Russians don't live where they are registered.

Rescuers, who worked through the night, focused Wednesday on reinforcing a wall to prevent it from collapsing as they removed the broken metal, shards of wood, crushed furniture and other debris.

Ruslan Novik, spokesman for the regional Interior Ministry, said 43 bodies had been identified. Two of the dead were pulled from the wreckage alive but died in the hospital, he said.

Police sought two men spotted by residents where the blast occurred, said Igor Avtushko, spokesman for the regional Interior Ministry. The men allegedly were carrying metal pipes and instruments, and police believed they opened the gas valves to steal the lids.

Thieves pilfer power lines, municipal facilities and industrial equipment throughout Russia in search of copper, bronze and other metals to sell for scrap.

Authorities found gas pipe lids missing in two neighboring buildings, Avtushko said, but crews were able to fix the gas leaks. NTV television said building residents had reported the smell of gas to local emergency officials before the explosion, but that gas workers didn't arrive in time. Novik said three other buildings had reported gas leaks, but he could not confirm the NTV report.

Andrei Seleznyov, 52, a resident of a neighboring building, said homeless people had been systematically stealing the lids in the past.

The General Prosecutor's Office said a gas explosion was the most likely cause of the blast, but it hadn't ruled out other possibilities. Security agents reportedly found no explosives. Neglect of safety precautions has led to frequent gas explosions in Russian apartment buildings and public facilities.

Tension is high in Russia after a series of deadly terrorist attacks blamed on Chechen rebels (search). Russia's Izvestia newspaper reported that many Interior Ministry officers had lived in the building that exploded, including those who had served in Chechnya, but at the time of the explosion only three were registered there.

Authorities in the region surrounding Moscow also are jittery after five recent attacks on gas and power lines, including one late Monday in which three supports holding a power line were damaged by an explosive device. A green Chechen separatist flag was found at the site, Russian media reported.