Updated

Mauritius has completed a frantic effort Thursday to drain the remaining oil on a leaking and stricken ship that is at risk of breaking in half.

The last of the 500 remaining tons of oil were removed from the MV Wakashio, which ran aground on a coral reef on July 25 -- but now environmentalists are worried about the 1,000 tons that spilled into the sea before the ship could be drained.

“Today we can confirm that there is just a small amount of oil left on the ship. We are not threatened with an even worse disaster,” Jean Hugue Gardenne, a communications manager for the Mauritian Wildlife Foundation, told The Associated Press.

This photo provided by the French Army shows oil leaking Tuesday from the MV Wakashio, a bulk carrier ship that ran aground off the southeast coast of Mauritius (EMAE/AP)

This photo provided by the French Army shows oil leaking Tuesday from the MV Wakashio, a bulk carrier ship that ran aground off the southeast coast of Mauritius (EMAE/AP)

MAURITIUS OIL DISASTER: RACE TO DRAIN STRICKEN SHIP BEFORE IT SPLITS IN HALF 

“However, make no mistake, the damage that has been done already is substantial. There is considerable clean-up work that must be done urgently," Gardenne said. "The damage to the coral reefs may be irreversible.”

Owner Nagashiki Shipping said in a statement that “residual” amounts of fuel remain on the ship. The company has sent experts to help in cleaning up the damage.

“We will continue to do our utmost to minimize the impact of oil spill recovery and environmental pollution,” said representative director Kiyoaki Nagashiki, a statement said.

An estimated 3,000 tons of fuel was removed from the ship, stranded on a coral reef at Pointe d’Esny, a sanctuary for rare wildlife. But the oil it has spilled has fouled the country’s coastline and the protected wetlands area, with Jugnauth declaring a national disaster.

Volunteers take part in the cleanup operation in Mahebourg, Mauritius, on Wednesday. (AP)

Volunteers take part in the cleanup operation in Mahebourg, Mauritius, on Wednesday. (AP)

MAURITIUS DECLARES EMERGENCY OVER OIL SPILL 

Prime Minister Pravind Jugnauth says Mauritius will seek compensation from Nagashiki Shipping, but the monetary value is unclear.

Nagashiki Shipping said it is investigating why the Wakashio went off course. The ship was supposed to stay at least 10 miles from Mauritius but instead came within a mile and struck the coral reef on July 25. Battered by heavy waves, the ship cracked and began to leak oil on Aug. 6.

Jugnauth’s government is also under pressure to explain why it did not take immediate action to empty the ship when it ran aground. Two weeks later, after pounding by waves, the ship cracked and began leaking.

Environmentalists on Monday had warned the ship could break apart “at any time.”

Thousands of students, environmental activists and residents of Mauritius are working around the clock trying to reduce the damage to the Indian Ocean island from the oil spill. (EMAE/AP)

Thousands of students, environmental activists and residents of Mauritius are working around the clock trying to reduce the damage to the Indian Ocean island from the oil spill. (EMAE/AP)

FLORIDA FISHERMAN SHARES UP-CLOSE VIDEO OF ENCOUNTER WITH GREAT WHITE SHARK 

As a result of the spill, some of the turquoise waters surrounding Mauritius were stained a muddy black, drenching waterbirds and reptiles with sticky oil.

Thousands of Mauritians have been working for days to reduce the damage by making improvised barriers from fabric and stuffed with straw and sugar cane leaves to try to contain the oil's spread. Others have scooped up oil from the shallow waters. It is estimated that nearly 400 out of the 1,000 tons that spilled have been removed from the sea.

The Wildlife Foundation is alarmed that the oil spill will ruin the work that it has done since 1985 to improve the area where the ship ran aground, Gardenne said.

“We have planted about 200,000 indigenous trees to restore the coastal forest," he told the Associated Press. "We re-introduced endangered birds, including the pink pigeon, the olive white-eye and the critically endangered Mauritius fody to the Isle aux Aigrettes. Now all this is threatened as the oil is seeping into the soil and the coral reefs.”

CLICK HERE TO GET THE FOX NEWS APP 

And, environmental group Greenpeace Africa warned that the consequences of the oil spill may be lasting.

“We know this disaster will have significant effects on biodiversity in Mauritius,” communications coordinator Tal Harris said. “There needs to be a detailed and urgent survey of the damage done and a monitoring program to see what can recover and how quickly, and how much residual oil sticks around in the long term."

The Associated Press contributed to this report.