The whale was spotted at about 7 a.m. Monday at Ocean Beach just north of Lawton Street, park service spokesman George Durgerian said.
Authorities believe the animal is either a fin whale, which is an endangered species, or a sei whale, and DNA tests are being done to conclusively determine the species.
Jim Oswald, spokesman for the Sausalito-based Marine Mammal Center, said scientists from the center took tissue and skin samples Monday. The DNA results will not come back for at least a couple of months.
The whale was badly decomposed when it was found, preventing authorities from conclusively determining its cause of death, but Durgerian said the animal had a slash along its back that "may indicate it was hit by a propeller" or another part of a vessel.
"Whether it hit it post-mortem or if it was alive is yet undetermined," he said.
The cause of death will likely not be determined, though, because crews spent most of today digging a 50-foot grave at the beach that the whale carcass will be moved into, hopefully by the end of the day, Durgerian said.
The whale was the second found dead in the Bay Area in the past week.
On Thursday, a whale carcass was dragged into the Port of Oakland by a container ship.
The animal, believed to be a minke whale, appeared to have been struck outside of the San Francisco Bay and dragged in on the bow of the ship.
Investigators believe the whale might have been dead before it was hit, based on what appear to be shark bite marks on it, according to the U.S. Coast Guard.
