SAN FRANCISCO -- Heavy morning fog slowed marine investigators early Friday as they attempted to piece together the circumstances surrounding the second collision between a vessel and a bumper protecting a Bay Area bridge in less than three months.

The barge Cascade, being guided by tugboats Delta Deanna and Pacific Wolf, was headed outbound from Rodeo when it hit the east piling of the west span of the Richmond-San Rafael Bridge while carrying 65,195 barrels of heavy black oil, according Coast Guard officials.

But unlike the environmental disaster triggered by the container ship Cosco Busan and the San Francisco Bay Bridge in November 7, 2007 no oil leaked into the Bay waters. .

An investigation into the incident was scheduled to begin at daybreak but weather caused a temporary setback, said Coast Guard Petty Officer Jonathan Cilley.

The California Department of Transportation arrived at about 7 p.m. Thursday to assess the damage to the bridge, Cilley said. The extent of the damage is unknown, although there was extensive damage to the barge, said Cilley.

The Coast Guard determined visibility of just 1-2 miles due to fog and a low ceiling, said Cilley. According to Coast Guard Lt. Anya Hunter, weather will be examined as part of the investigation.

Alcohol tests were administered to the crewmembers and none had been drinking prior to the incident, said Hunter. Drug tests were also administered but the results are pending.

The Coast Guard, Caltrans, the California Highway Patrol, the California Department of Fish and Game, a Marin County Hazardous Materials team and the San Rafael Police Department are assisting in the investigation.