“What we’ve been told at this point, was that there was nothing concrete,” Multnomah County Sheriff’s Deputy Travis Gullberg said.

The carcass was discovered two days after the widely reported discovery of six dead sea lions enclosed within floating traps just below Bonneville Dam. Authorities said they remained clueless about the deaths of the six animals at Bonneville.

Mark Oswell, a spokesman for the National Marine Fisheries Service in Silver Spring, Md., told the Associated Press Thursday that based on information so far “there is nothing to indicate a need to do toxicology tests,” which could determine if poison was involved.

Brian Gorman, a fisheries service spokesman in Seattle, offered no insight about why investigators would rule out toxicology tests.

“It’s the lack of clues that is slowing folks down,” Gorman said. “It would be nice if you opened the animal and its chest was full of blood. There wasn’t anything that jumped out at anyone.”

As for the animal discovered between Vancouver and Portland, authorities can’t rule out a death by natural causes.

After a biologist examined the carcass on Wednesday, Gullberg said, the remains were buried near the sheriff’s river patrol office along the Columbia River shoreline near Portland International Airport.