MARIN COUNTY -- San Francisco's north shore beaches are safe for recreational use following Thursday's 2.7 million gallon sewage spill in Marin County, city officials announced Monday.

A San Francisco Public Utilities spokesman said today that water quality tests over the weekend revealed below-normal bacteria levels and "no public health concerns."

Signs posted on Friday warning against entering the water at Crissy Field, Baker Beach, Aquatic Park and China Basin beaches are being removed, according to the SFPUC.

The signs had been posted as a "proactive, precautionary response" to Thursday's spill of partially treated wastewater into Richardson Bay, according to the SFPUC.

Sewage and storm water was accidentally released into Richardson Bay by the Sewerage Agency of Southern Marin between 5:30 p.m. and 8:30 p.m. Thursday, officials reported.

A failed pump at the agency, located at 450 Sycamore Ave. in Mill Valley, caused the spill, according to the Marin County Sheriff's Office. An alarm system designed to alert officials of the pump malfunction also failed, the sheriff's office reported.

In a statement accompanying the SFPUC announcement, Mayor Gavin Newsom said such incidents "remind us of the economic and recreational importance" of area beaches and waterways.

Friday's testing showed two locations with contamination levels above the state fecal coliform standard for water contact recreation, according to the operations center.

Almost all samples taken from locations throughout the bay Saturday were within the state standard, officials said. Only one location, Bay Front Office Park, had results above the state standard, but had reduced since Friday.

Sen. Carole Migden, D-San Francisco, announced Sunday she will request an investigation into the cause of the delayed notification and how to eliminate similar breakdowns in communication.

"We cannot prevent natural disasters or just plain bad weather, but we must assure our communities we are fully prepared and have our emergency systems fully operative and properly run especially when an environmental or human health hazard occurs," Migden said in a prepared statement.

Public safety information regarding the spill is available online from the Marin County Sheriff's Office at www.marinsheriff.org.