Hundreds of fish, crabs and shrimps found floating in Jiaozhou Bay were not killed by crude oil pollution, the environment protection bureau in Qingdao, Shandong province, said, China News Service reported.

In a written statement to local media and fishermen, the environment body said a thorough investigation had immediately been launched and findings indicated that the fish had not been killed by oil pollution.

"We found little crude oil floating on the sea surface," the statement said.

The marine life, raised by local fishermen, may have perished from lack of oxygen as the sea had frozen over, the statement said.