The six sea lions that died in traps at Bonneville Dam a week and a half ago likely died of heat prostration, or heat stroke.
That's according to results released Wednesday from the necropsies of the 6 animals.
Initially, officials with the federal fisheries service thought the animals had been shot inside closed traps.
After that, the federal government announced it would shut down its controversial sea lion trapping program. Officials had started trapping and removing the animals to keep them from eating so many endangered salmon.
Brian Gorman is a spokesman for NOAA Fisheries in Seattle. He said the new results were pretty consistent that heat stroke was the cause of death, but the big mystery is how the trap doors were closed.
Brian Gorman: "What the animals died from seems to be solved. But the mystery of how the trap doors got closed is still under investigation and still has some of us scratching our heads."
Gorman said officials may learn more from analyzing tissue samples from the dead animals. Those results could be available in 10 days.