Scientists are examining the deaths of at least six dolphins and over 100 sea turtles along the U.S. Gulf Coast in recent weeks to see if they are victims of the giant oil spill in the region, wildlife officials said on Thursday.

All of the deaths are being looked at as possible casualties of the oil gushing unchecked since April 20 from a ruptured wellhead on the floor of the Gulf off Louisiana because of their proximity in time and space to the spill.

But none of the dolphins or turtles examined showed any obvious visible signs of oil contamination.