SAN FRANCISCO -- Crews were continuing to clean areas affected by last week's oil spill into the San Francisco Bay, though for the second day no oil sheen was visible on the water Monday, a U.S. Coast Guard petty officer said.

Between 400 and 800 gallons of oil leaked into the Bay from the Panamanian-flagged tanker "Dubai Star" after the vessel's transfer system equipment had a mechanical failure while conducting bunkering operations with a fuel barge about two miles south of the Bay Bridge early Friday morning.

About 54,500 feet of boom was placed around the oil, and it was reported Sunday afternoon that the sheen was no longer visible, Coast Guard Petty Officer Larry Chambers said.

The Dubai Star has been anchored at Pier 80 in San Francisco to have its hull cleaned, Chambers said.

As of Monday morning, wildlife specialists have recovered 36 live birds affected by the oil and 11 dead ones, Chambers said. Two of the 36 live birds collected have since died.

Cleanup crews Monday were focusing their cleanup efforts on Robert Crown Memorial State Beach, Ballena Bay and Bay Farm Island in Alameda. Robert Crown Memorial State Beach remains closed to the public, according to Chambers.

Anyone who spots an oiled animal should call (877) 823-6926 and not attempt to rescue it.