The six whales washed up between May 21 and 28. The first, a yearling gray whale, washed up in Bolinas, in Marin County, on May 21. A partial necropsy that was conducted May 23 was inconclusive and the whale’s cause of death remains unknown, CalAcademy said.

Six dead gray whales have been found in the San Francisco Bay Area over the last week, officials said Wednesday, in a year in which there has been an unusually high number of sightings in the area.