Workers and officials look over a crater caused by a massive explosion in a mostly residential neighborhood in San Bruno, Calif., Friday, Sept. 10, 2010. At least 50 people were hurt, with three suffering critical burns in the explosion Thursday evening that left a giant crater and sent flames tearing through the middle-class neighborhood of 1960s-era homes in hills overlooking San Francisco, the bay and the airport. (AP Photo/Jeff Chiu)