The environmental group Greenpeace says it believes an oil spill in northeastern China was up to 60 times larger than has been reported.
Richard Steiner, a marine conservation expert from the University of Alaska, announced the conclusion Friday after a 10-day on-site investigation.
Steiner estimates the July 16 explosion at an oil terminal in Dalian released 60,000 to 90,000 tons of crude oil into the South China Sea, making it larger than the 1989 Exxon Valdez spill in Alaska. Official estimates have said only 1,500 tons of crude were spilled.
The explosion ruptured two pipelines and ignited a fire that raged for 15 hours. Greenpeace said Chinese workers told the group they deliberately released additional oil into the sea to contain the fire and reduce the risk that a nearby tank of dimethylbenzene would explode.
Steiner said at a Beijing news conference that the explosion and fire completely destroyed one oil tank with a capacity of 90,000 tons. He said Greenpeace was told that the tank had been filled shortly before the blast.
He said a spill of that size would rank among the 30 largest ever recorded.
The oil spill expert, engaged as a consultant by Greenpeace, said Chinese crews have already recovered more than 1,500 tons of oil - the amount officially said to have been spilled.
Reuters news agency contacted PetroChina on Friday but said officials of the company, which operates the oil storage facilities at Dalian, could not confirm or deny the Greenpeace findings.
Some information for this report was provided by AP, AFP and Reuters.
