A 32-foot gray whale that turned up dead under the Washington state ferry terminal in downtown Seattle died earlier this week because it was struck by the propeller of a large vessel.

A necropsy completed Saturday found large, deep gashes on the whale's right side and back, indicating the cause of death.

Biologists estimated the time of death as no earlier than Monday and likely on Tuesday. They said the animal likely died quickly. It was found late Wednesday.

The juvenile female whale was about two to three years old. She was just over 30 feet long and had been in very good health before death because its blubber was thick, with healthy amounts of oil.

Biologists are not sure why the whale entered Puget Sound, since most gray whales have already migrated south.