Both main-line tracks at an Oakland train station reopened Thursday morning following a train crash that involved two Amtrak trains, injuring 18 people, but there may be “minimal delays through the morning hours,” Washington Post reported.

Federal officials have started an investigation which will last three to six months. Amtrak and Union Pacific Freight Railroad, the owner of the tracks, pledged to cooperate with the investigation, according to Amtrak.

The investigation will include examining the wreckage, interviewing crew members and checking any radio or cellphone exchanges with dispatchers, Federal Railroad Administration spokesman Warren Flatau said.

An Amtrak train was traveling at an estimated 15 to 20 mph when it crashed another stationary Amtrak train around 10 p.m., Wednesday. While one passenger Alton Smith said he felt an awful jolt from the impact, another person Miesha Anderson heard a big bang, like a bomb. Anderson said she thought a forklift had struck the train. We didn't even think that another train had hit the train, she told CBS5.

“The train traveling should have never continued past the red signal,” an Amtrak representative said. The train went through a red light without braking, Oakland Fire Department battalion chief Emon Usher was told. The speeding train then ran into the stationary one, from which passengers were getting off.

The wheels of each lead engine went off the track, Amtrak spokesman Cliff Cole said.

Several injured people were taken to local hospitals afterwards. One of them suffered a broken arm. Some were deliberately immobilized by emergency medical personnel as a precaution against spinal injuries. However, officials said all the injuries were minor and non-life-threatening.

Less than two weeks ago, there was also a significant incident in the San Francisco East Bay area involving injuries to Amtrak passengers.

An Amtrak passenger train ran into a truck at a railroad crossing near Brentwood where there were no lights or gates, resulting in 39 people include two crew members on the train, suffering minor to moderate injuries.