SAN FRANCISCO (KGO) -- A team of eight people from the National Transportation Safety Board has arrived in San Francisco to investigate a gas line explosion that damaged multiple buildings.
RELATED: PG&E repairs gas line, works on restoration after San Francisco gas explosion
The NTSB says it's very early in the investigation, but they will begin interviewing witnesses this morning. They also say they'll be collecting perishable evidence, including a section of the pipeline, looking into the training of the workers, and what happened at the time of the explosion.
"There was an explosion. We need to figure out why it happened, how it happened, and we want to prevent it from happening again," said NTSB Board Member Jennifer Homendy.
The NTSB says the team is typically on scene for 7 to 10 days for incidents like these. They will evaluate the accident and then issue recommendations to address the safety issues.
RELATED: Residents rushed to evacuate amid gas explosion, fire on Geary Boulevard in San Francisco
PG&E says a third party engineering firm breached a four-inch gas distribution line and that they had a valid Underground Service Alert ticket. Verizon hired the third party engineering firm MasTec to install fiber optic cables. A PGE locator responded to the area on January 28 and properly marked the underground lines. PGE says the markings were captured with photo documentation.
PG&E says it took them almost two and a half hours to shut off gas because they had to hand dig to pinch the line and they didn't want to disrupt gas service to many more customers.
VIDEO: Audio captures terror after gas explosion, fire in San Francisco
The California Public Utilities Commission is also investigating.
The Hong Kong Lounge II restaurant was damaged in the fire and loyal customers have started a GoFundMe page for employees.
Take a look at full coverage on the gas explosion and fire on Geary Boulevard in San Francisco.