A massive whale that washed up along the Mendocino Coast south of Fort Bragg Monday evening likely was struck by a hydrographic vessel earlier in the day.

The vessel reported hitting a whale about seven miles off the coast of Fort Bragg Monday afternoon, said Joe Cordaro, a marine biologist with the National Oceanic and Atmospheric Administration.

"It's more than a coincidence," he said Tuesday.

The dead whale has a gash in its back that a Coast Guard official estimated was more than 8-feet long.

Cordaro did not have information on the vessel that collided with a whale but expects its crew to submit a report within two days, as required by law.

While it was unclear Monday night whether the whale was alive, it was obvious Tuesday morning that the huge mammal — estimated to be more than 70-feet long — was dead, said Larry Wagner, who lives on the bluffs overlooking a cove where the carcass is located.

Both Wagner and Cordaro believe it's a blue whale, the largest of all mammals.

Humboldt State University officials will be sending students from its marine program to evaluate the whale, Cordaro said.

A member of the Marine Mammal Center in Marin County tried to find and evaluate the whale Monday night but was unable to locate it, said spokesman Jim Oswald.

The ocean inlet where it's located is inaccessible, so all the Humboldt State students may be able to do is estimate its size from the overlooking cliffs, Cordaro said.

This is the second blue whale reported to have been killed by a ship's propeller along the California coast this year, Cordaro said. It's more common for other, more abundant types of whales — such as gray and fin whales — to be killed, he said.

The other blue whale was found along the Big Sur coastline last week, he said.

Boat-related blue whale deaths occur sporadically. There were four in 2007, all in the Santa Barbara channel, and none last year, Cordaro said.

This is the first one reported to fisheries officials so far north on the California coast, Cordaro said.

"Not to say it doesn't occur," he added.

He said there have been increasing reports of blue whales being spotted off the coast of California.

"That may be a factor," he said.

The whale will be left where it is. If it becomes a nuisance, the people who own the property adjacent to the ocean will be responsible for dealing with it, Cordaro said.

The whale carcass currently is in an inlet adjacent to private property, part of a gated community south of the Fort Bragg Botanical Gardens.