FLORENCE, Ore. – Authorities on Sunday were trying to figure out what caused the death of a whale that beached itself near Florence after struggling in shallow water a day earlier.

Jim Rice of the Marine Mammal Stranding Network planned to collect a tissue sample from the dead whale, which was spotted Saturday on a remote area of a rocky beach near Heceta Head.

Marine biologists originally thought it was a sei whale. But Rice said Sunday that after examining the whale up close, it was actually a 50-foot-long fin whale, which is the second-largest whale species after the blue whale. The fin whale is endangered, and it is very rare to see one wash up on shore.

The fin whale was the same one seen Friday struggling in waist deep water north of Florence before freeing itself and swimming away hours later.

“This animal was probably chronically ill for some time," Rice said. "It did appear to be underweight, which means it probably hadn't been feeding properly. It was probably either sick or injured for quite some time before it made its way close to shore and eventually stranded,” Rice said.

The whale had a bleeding sore or wound of some kind near its tail. Rice has said he did not believe the whale was attacked or hit by a ship, however.

A whale of that size has only two types of predators: killer whales and humans.

“It does not appear to be an area on the body where one would expect a ship strike," he said. "It's at the underside of the body, and generally a whale would not get hit at the underside. It would likely get hit on the back."

Rice said sharks likely would not bother going after an animal of that size.

Meanwhile, officials on Sunday were trying to figure out what to do with the carcass. State officials closed Heceta Head State Scenic Viewpoint and the Devil's Elbow beach north of Florence on Sunday over concerns for traffic safety and the need to protect the whale carcass.

Tampering with a whale carcass -  removing pieces or altering it in other ways - is prohibited by federal law, authorities said.

Decades ago, state officials had a similar dilemma on their hands at a Florence-area beach and decided to use explosives to obliterate a whale carcass. That did not turn out so well. To watch KATU's famous "Exploding Whale" coverage, click here.