Coast Guard investigators are trying to determine what caused an oil tanker to strike a tower of the Bay Bridge Monday morning. Around 11:20 am, the tanker Overseas Reymar clipped the so-called "echo" tower on the far east side of the bridge's western span.

The tanker was damaged, but there are no reports of spilled oil or injuries. San Francisco Bar Pilots spokesman Charles Goodyear says there was a bar pilot on board.

Monday's incident marks the second time in slightly more than five years that a ship has scraped a tower on the Bay Bridge's western span. In 2007, the container ship Cosco Busan struck a different support tower, spilling bunker fuel into the Bay. After that crash, Caltrans updated a fender protecting the bridge and the state tightened bar pilot rules.

Host Stephanie Martin talks with Paul Rogers, managing editor of KQED Science, who is following the story for KQED and for the Mercury News.