At least 20 sea turtles have been found dead along a 50km stretch of coast in the American state of Mississippi.
Hundreds of thousands of litres of crude oil is spewing into the Gulf of Mexico from a BP oil well that exploded and sank at the end of April.
State authorities say no oil was found on the turtles but they may have died after eating oil-coated fish, the ABC reports.
Meanwhile, US officials are considering throwing open dams in a desperate bid to flush oil out of the Gulf of Mexico.
The US Coast Guard says the dams could boost the flow of water into Alabama's Mobile Bay, which then enters the Gulf.
BP vows to clean up spill
Oil giant BP has acknowledged it is "absolutely responsible" for cleaning up the huge oil spill.
However, BP boss Tony Hayward said the firm was not to blame for the accident which sank the Deepwater Horizon rig on 22 April, causing the slick, and the equipment that failed belonged to drilling firm Transocean.
Both companies are expecting lawsuits over the slick, the BBC reports.
US President Barack Obama has described the oil leak as a "potentially unprecedented" environmental disaster.
"BP is responsible for this leak. BP will be paying the bill," he said.
Schwarzenegger reverses drilling support
The governor of California, Arnold Schwarzenegger, has withdrawn his support for offshore oil drilling in the light of the Gulf calamity.
Mr Schwarzenegger, who last year pushed for more oil drilling off the coast of California, says he changed his mind about the safety of offshore oil platforms after seeing pictures of the current oil slick on television.