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, according to the initial results of a necropsy completed Saturday.

The necropsy found large, deep gashes on the whale's right side and back, indicating the cause of death. The gashes extended into the whale's body cavity and the propeller's force had sheared off one of its ribs.

Biologists estimated the time of death as no earlier than Monday and likely on Tuesday. They said the animal likely died quickly, probably within an hour.

The whale's body was discovered under the Colman Dock ferry terminal late Wednesday. Ferry service wasn't affected, but people reported a foul odor.

The examination also found that the whale was a juvenile female, 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 along the outer Washington Coast.

Gray whales spend their summers feeding in Alaska. Each fall, they travel along the Pacific coast from Alaska to Baja California, Mexico, said Michael Milstein, a spokesman with the National Oceanic and Atmospheric Administration Fisheries Service.

Gray whales were removed from Endangered Species Act protection in 1994 and the population along the West Coast is considered recovered. But the whales are still protected by the Marine Mammal Protection Act.

In the next few, days the whale's remains will be towed away from shore and sunk to decompose naturally.

The results of the necropsy will be assessed by NOAA Fisheries scientists and will be relayed to NOAA Fisheries' Office of Law Enforcement for possible investigation.