ARCH CAPE — Researchers gathered in Falcon Cove were prepared to conduct a necropsy of the humpback whale washed ashore Friday night. Although the whale had been dead for several days, they hoped the examination would provide clues as to the mammal’s demise.

But when they arrived at the secluded and tide-driven Cove Beach, the whale was gone. “The whale washed back out,” Tiffany Boothe of the Seaside Aquarium said. “It probably will wash back in deeper into the Cape Falcon Marine Reserve — an area we can’t access because of the boulders.”

The carcass could wash up on another beach or it could “rot away” somewhere, the aquarium’s General Manager Keith Chandler added.

Chandler, Boothe and a team of researchers from Portland State University were prepared to examine the whale, which was swept ashore Friday, its stomach distended.

“That big thing was its stomach,” Chandler said, referring to what looked like a giant hot-air balloon before it deflated midday Saturday. “By the time I saw it, it had already exploded.”

Chandler said the stench on Saturday was “horrible.”

“The stomach was inverted,” he said. “The water was murky, muddy, brown — I think it was the stomach contents that were smelling so bad.”

By Sunday, though, the smell was gone, he said.

Humpbacks are less common than gray whales, and occasionally wash up on the North Coast.

As for what caused the whale’s death, that remains a mystery.

If the whale washes up between here and Tillamook, Chandler and Boothe said they will be out once again. They cover the coast from Tillamook to the end of Long Beach, Washington. If the whale floats farther south, it will be out of the aquarium’s jurisdiction and monitored by the Hatfield Marine Science Center in Newport.

Lyra Fontaine contributed to this report.