U.S. Coard Guard investigators say they are looking at human error as the cause of a Chinese cargo ship's collision with a bridge in San Francisco.
Last week's accident did not damage the bridge, but the impact opened a 30-meter gash in the vessel's hull, puncturing two fuel tanks and spilling more than 200,000 liters of thick bunker oil into San Francisco Bay.
California has ordered an emergency cleanup of the bay and its oil-coated shoreline, and nearly 800 people are working to rescue birds, fish and other wildlife from potentially deadly pollution.
The Coast Guard says preliminary investigations show no mechnical failure on the ship, so officials are trying to determine whether it was traveling too fast at the time of the collision last Wednesday, in a heavy morning fog.
They also are checking communications between the ship's Chinese crew, the American harbor pilot who was on board the Cosco Busan, and the local Coast Guard station monitoring ship traffic.
By late Sunday, cleanup crews had recovered about one-third of the spilled oil, but the effort is expected to continue for weeks or months.
Some information for this report was provided by AP and Reuters.