Federal officials on Thursday began investigating an Oakland train crash involving two Amtrak trains that injured 17 people.
The investigators will examine equipment, interview crew members and check any radio or cellphone exchanges with dispatchers as part of the probe, according to Federal Railroad Administration spokesman Warren Flatau.
Flatau said the investigation could take between three and six months to complete.
The crash occurred around 10 p.m. Wednesday when an Amtrak train ran into a train that was unloading passengers at an Oakland station.
Seventeen people suffered minor injuries, according to Amtrak. Company spokeswoman Vernae Graham said seven of those people were taken to hospitals, where they were treated and released.
The train was traveling an estimated 15 to 20 mph when it struck the stationary Amtrak train, Oakland Fire Department battalion chief Emon Usher said.
Usher said company officials told him the train went through a red light.
"According to the Amtrak representative, the train traveling should have never continued past the red signal," Usher told The Associated Press.
Graham, citing the ongoing investigation, said she could not comment on the report of the train running a red light or any other possible factors in the crash.
Amtrak officials have described the crash as a "low-speed" collision between Amtrak's "San Joaquin," a train that operates between Bakersfield to Oakland, and Amtrak's Coast Starlight, a train from Los Angeles to Seattle.
The wheels of each lead engine went off the track, Amtrak spokesman Cliff Cole said.
Amtrak and the owner of the tracks, Union Pacific Freight Railroad, will work with federal officials to investigate the crash, according to Amtrak.
Authorities originally reported 16 injuries in the crash, but the company arrived at the higher figure after compiling numbers overnight, Cole said.
Alton Smith, a passenger on one of the trains, told television station KTVU he felt an "awful jolt" from the impact.
Another person, identified by television station CBS5 as Miesha Anderson, told the station she heard a "big bang, like a bomb." She told the station she thought a forklift had hit the train.
"We didn't even think that another train had hit the train," she said.
A couple of hours after the crash, about 50 passengers were gathered inside the train terminal, talking to Amtrak officials, while Amtrak and local officials inspected the two trains.
Service at the station was restored Thursday morning.
The crash is the second significant incident in two weeks in the San Francisco East Bay area involving injuries to Amtrak passengers.
On Sept. 30, 37 passengers and two crew members suffered minor to moderate injuries when an Amtrak passenger train collided with a truck at a crossing near Brentwood where there were no lights or gates.
The truck's driver and passenger were not hurt.
Associated Press writer Sudhin Thanawala and broadcaster Sofia Mannos in Washington contributed to this report.