Scientists were at a loss Friday to explain the mysterious deaths of more than 70 green turtles that have washed up on beaches in northeast Australia over the last week. Queensland state authorities said 62 of the vulnerable species were confirmed dead and another 10 were spotted floating at sea by a helicopter. Marty McLaughlin, operations manager at Queensland Parks and Wildlife Services, said the turtles were nourished and had no obvious signs of illness. \"There is no obvious cause of death. We\'ve tested for all the normal reasons, like boat strikes and starvation, but that has not occurred,\" he told AFP. \"It is species-specific to green turtles and we can\'t see any signs of toxicity or chemicals, and our analysis to date has shown no parasites. It\'s a complete mystery.\" All of the turtles were found around Upstart Bay, south of Townsville, in the past week. McLaughlin said crabs and pigs feeding on the carcasses did not appear affected by whatever killed the turtles, which are considered vulnerable under national legislation.