The U.S. prosecutors opened a criminal investigation about the Chinese container that crashed last Wednesday causing a massive oil spin in San Francisco.

Admiral Thad Allen, the head of the U.S. Coast Guard told to reporters in San Francisco on Sunday that his agency is investigating the cause of the crash together with the U.S. Attorney’s office. For the moment, the container is staying in Oakland for repairs as Allen told reporters on Sunday night.

The Cosco Busan, one of the China COSCO Holdings Co LTD’s containers left the Port of Oakland at 6:31 in the morning and two hours later hit a fender around a support tower due to the limited visibility caused by the foggy weather, according to Reuters at that time. 58,000 gallons of oil were poured in the bay.

The U.S. Coast Guard was forced to close four beaches near San Francisco to clean up the mess. Almost 60 ships and 800 workers were involved in cleaning the area recovering nearly 12,271 gallons of oil so far, while another 4,000 gallons has evaporated in the air and nearly 200 dead birds have been recovered, officials said.

Sen. Dianne Feinstein, a former San Francisco mayor said at a news conference that “this incident should not have happened. I think we can improve the system to manage shipping traffic in and out, in all kinds of weather conditions," Reuters reports.

On a preliminary investigation petty Officer, Mariana O’Leary said that there was nothing mechanically wrong with the vessel.

The National Transportation Safety Board launched an investigation into the cause of the crash.

Democrat Barbara Boxer is very concerned about the way the investigation is going. In a letter to Allen on Thursday, she said: "I am very troubled by the Coast Guard's delay in delivering accurate information to the public and to the city of San Francisco," CNN reports.

Governor of California Arnold Schwarzenegger toured the area himself and called the spill a state of emergency on Friday.