SAN FRANCISCO (CBS SF) – One day after an Amtrak train derailed in Philadelphia, killing seven people, officials said the engineer who was behind the controls had previously worked on commuter rail in the Bay Area.

The engineer, identified as Brandon Bostian, worked for Caltrain several years ago. According to the San Francisco Chronicle, Bostian worked as an engineer for the rail system between 2010 and 2011. Caltrain contracted with Amtrak at that time.

Investigators said they have interviewed the 32-year-old and taken a blood sample to check for drugs or alcohol. They’re also reviewing his phone records, to determine if he was texting or on the phone at the time of the crash.

On Wednesday, crews began removing the twisted wreckage from the crash site, taking it to a secure location for further inspection.

Investigators said Bostian hit the brakes just moments before the train flew off the rails Tuesday night. The NTSB said the train was traveling more than twice as fast as it should have been:

“Maximum authorized speed through this curve was 50 miles per hour. When the engineer-induced brake application was applied, the train was traveling at approximately 106 miles an hour,” said NTSB board member Robert Sumwalt.

The crash took place at 9:21 p.m. Eastern Time Tuesday night. The locomotive and all seven cars tumbled off of the rails, killing at least seven people and injuring hundreds more.

Police in Philadelphia says Bostian refuses to give a statement and left a precinct office with a lawyer.

Investigators are now reviewing information from the train’s data recorder and footage from its forward-facing camera.