OAKLAND, Calif. -- The lead cars of two Bay Area Rapid Transit trains derailed and 13 people sustained minor injuries Tuesday afternoon after a collision just outside the busy 12th Street station in the heart of downtown Oakland.

One train sideswiped another at about 3 p.m. in the "minor collision," BART spokesman Jim Allison said. There were no significant delays as of 7:10 p.m., but crews were expected to remain in the area through the night to put the trains back on the rail.

Oakland fire Lt. David Brue said 13 people were taken to local hospitals to be treated for minor injuries.

The two trains, which were carrying a total of about 300 passengers, were traveling slowly when they collided because BART trains usually travel at minimal speeds in that area, BART spokesman Linton Johnson said. The 12th Street station is a busy hub where several lines merge and many passengers switch trains.

"Passengers said they barely felt the impact," Johnson said.

However, some passengers were placed on stretchers and were taken up elevators and escalators from the underground station to ambulances that were waiting at street level on Broadway.

Johnson said all passengers were evacuated shortly after the collision except for one person who was on a wheelchair. Firefighters successfully removed that passenger.

One of the trains was traveling from the West Oakland station to Pittsburg/Bay Point and one was coming from the Lake Merritt station to Richmond.

They were traveling in the same direction, so the collision was a side-to-side collision and wasn't a head-on crash, Johnson said.

One of the trains was being operated manually and one was being operated automatically by a computer. The front cars of both trains derailed.

Both train operators have submitted to drug and alcohol tests. The accident had little effect on the evening commute. BART was able to reroute trains around the affected tunnel while passengers evacuated and safety inspectors launched their investigation.

BART spokesman Johnson tells KTVU the agency will bring in heavy equipment after the station closes Tuesday night to move the train back on to the track so it can be removed.

BART is hoping to have the trains cleared by the morning commute, Johnson said.