(San Francisco, CA) -- There's a lot of cleaning up going on off part of the California shore.
There was an oil spill in San Francisco Bay on Friday, and crews are still trying to clean up the mess.

The spill happened when a line ruptured on an oil tanker during a fuel transfer.
Now six miles of shoreline are off-limits, except to cleanup crews that are protected by hazmat outfits.

They're scooping up oil tar balls from the sand. Others have been cleaning up birds, which have oil-coated wings.
So far, thirteen birds are dead, but volunteers have saved 36.

Now, investigators are looking at whether the ship's crew broke any laws during the spill, which happened while the ship was refueling.

They say the ship leaked crude into the bay for about four hours before the crew discovered the spill.