BY GARANCE BURKE and PAUL ELIAS

Associated Press Writer

SAN FRANCISCO

The 752-foot Overseas Reymar from the Marshall Islands rammed the tower about 11:20 a.m. as it headed out to sea, according to the Coast Guard and state transportation officials. The impact didn't affect traffic on the busy bridge--the main artery between San Francisco and Oakland, Ney said.

The parent company that owns the ship, OSG Ship Management Inc., said the accident occurred as the vessel hit an underwater portion of the massive bridge structure.

Investigators late Monday had not determined the cause of the crash.

"There's always the human factor," Coast Guard Lt. Cmdr. Shawn Lansing said. "That is again what we'll look into and see whether, in fact, it was a human error or something else and take that into consideration in the development of future regulation."

Visibility at the time of the collision was about a quarter-mile, but officials didn't say if that was a factor.

There was no timetable for completing the investigation, Lansing said. The crew and captain of the ship will undergo drug and alcohol testing, per federal regulations. Inspectors also will examine the hull of the ship above and below water, Lansing said.

The mishap damaged about 30 to 40 feet of fender of steel and wooden timbers built onto the span to absorb the brunt of a ship's collision, said California Department of Transportation spokesman Bart Ney.

The incident brought back memories of a major crash in 2007 that spilled 53,000 gallons of oil into the bay. Oil leaking from the Cosco Busan contaminated 26 miles of shoreline, killed more than 2,500 birds and delayed the start of the crab-fishing season.

The Overseas Reymar was not carrying oil as cargo on Monday, only fuel to power its engines, said Charlie Goodyear, a spokesman for the San Francisco Bar Pilots Association.