SAN QUENTIN, Calif -- Untreated sewage that leaked from the San Quentin State Prison into San Francisco Bay Thursday morning spilled into a prison parking lot before reaching the water, and not all of the estimated 1,500 gallons spilled made it in the bay, according to initial reports from the Marin County Sheriff's Office of Emergency Services.

Authorities said a pump station malfunction caused sewage to leak from a manhole cover into a parking lot on the northeast end of the prison, said Brian Crawford, assistant director of the county's Community Development Agency.

Some of the 1,500 gallons then flowed into the bay, but officials do not know the exact amount, Crawford said.

Prison officials responded to the spill, reportedly sandbagging the area to keep some of the sewage from reaching the water, Crawford said.

The State Department of Corrections reported the spill at 10:50 a.m. to the State Office of Emergency Services, and then contacted the Marin County Environmental Health Services at 11:15 a.m., according to the Marin County OES.

State hazardous materials specialists took water samples from the spill area and expect to have initial water quality test results Friday afternoon, Crawford said. Additional samples will be collected Friday for more testing, he said.

Department of Corrections officials reportedly disposed of sewage left in the parking lot and contained the release from the manhole, Crawford said.

The Marin sheriff's marine patrol was dispatched to Point San Quentin to warn windsurfers and kayakers, and signs have been posted in popular boating and windsurfing access points including Point San Quentin, the Corte Madera Creek, and the Greenbrae Boardwalk area, Crawford said.