WASHINGTON (CNN) -- A National Transportation Safety Board team was on its way to California Saturday to probe why a container ship struck the San Francisco-Oakland Bay Bridge earlier this week, spilling 58,000 gallons of oil into the water.
Crews work Thursday to remove oil from a beach on the San Francisco Bay.
The oil -- heavy-duty bunker fuel from the 900-foot-long ship -- has spread along the San Francisco city waterfront and out of the San Francisco Bay, beneath the Golden Gate Bridge toward Marin County.
Authorities closed several beaches and shorelines to the public because of health concerns.
They also banned fishing in key locations on Port of San Francisco property. See a map of the affected areas »
Dozens of birds have died since the spill, the Coast Guard told The Associated Press.
The California Department of Fish and Game said it had rescued six oiled birds.
The Oil Wildlife Care Network -- a group of California wildlife care providers and regional facilities -- said it had received 94 live birds affected by the spill, as well as two dozen dead.
But that's likely just the tip of the iceberg.
There have been hundreds of sightings of oiled birds in the area, according to the AP. Officials scrambled to rescue as many as possible. See photos of the spill and its impact on wildlife »
"Oil and feathers don't mix," Yvonne Addassi, a wildlife biologist with the state Department of Fish and Game, told the AP.
"We're in a time crunch. The birds can only stayed oiled for so long before they can no longer be rehabilitated."
There was heavy fog when the MV Cosco Busan hit a shield surrounding a support tower of the bridge Wednesday. Watch the damage to the tower and ship »
"We're going to learn from this case, we're going to prevent the next one, if at all possible, and if there are people responsible or accountable ... they'll be held accountable," the Coast Guard's Rear Adm. Craig Bone said during a news conference Saturday.
It was not unusual for the NTSB to send a team to investigate, he said.
"Any type of incident that is large in nature and has large catastrophic consequences, we counsel with NTSB to discuss whether or not that type of investigation is warranted," Bone said.
Meanwhile, a member of Congress expressed her uneasiness to the Coast Guard about its handling of the collision and resulting spill.
"I am deeply concerned about the recent news reports that the Coast Guard had underestimated the severity of the spill and after learning of the spill's true size failed to report that information for more than four hours," Sen. Olympia Snowe, R-Maine, said in a statement Saturday.
She is the ranking member of the Senate Subcommittee on Oceans, Atmosphere, Fisheries and the Coast Guard.
Snowe's letter questioned Commandant Thad W. Allen on those news reports, the statement said.
On Thursday, the Coast Guard said it had recovered about 8,000 gallons of oil from the spill.
The collision didn't do any structural damage to the bridge -- which carries more than 250,000 vehicles daily -- and there was no interruption of traffic, the California Department of Transportation said.
The Cosco Busan was outbound from Oakland when it came in contact with the tower supporting the western suspension span of the Bay Bridge, the Coast Guard said. It moored near Treasure Island, which the bridge crosses, after the accident.
It was "highly likely" that the thick fog blanketing the bay in the early morning hours contributed to the accident, Coast Guard Petty Officer Kevin Neff said. E-mail to a friend
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