Rescue workers combed their way through the mangled wreckage of a commuter train late Friday looking for survivors after a commuter train collided with a freight train in suburban Los Angeles. At least 10 people were confirmed dead, with another 107 injured, 40 critically, officials said. Authorities fear the death toll may rise. The Metrolink train, packed with about 220 rush-hour commuters, collided head-on with a Union Pacific freight train about 4:30 p.m. (7:30 p.m. ET) Friday in Chatsworth, a northwestern suburb of Los Angeles. "It was like running into a brick wall at 60 miles an hour," an injured passenger said. Officials could not immediately say how the two trains ended up on the same track. The collision sparked a fire that hampered firefighters from getting to the front commuter car, where most of the injuries occurred, Los Angeles County sheriff's spokesman Steve Whitmore said. The blaze was eventually brought under control. Watch a report on the collision. Late Friday, firefighters climbed through windows into a commuter car that was turned on its side, with part of the train's engine pushed inside it. Two others remained upright. The rescue effort is expected to continue at least into the daylight hours, Whitmore said. "We've already found survivors trapped under fatalities," Whitmore said. The media relations department of the Los Angeles police department said one LAPD officer was among those killed, but did not release additional details. "That number will likely grow because, as you know, we are in a rescue phase," said Los Angeles Mayor Antonio Villaraigosa. Among the 107 injured, 40 were so critically hurt that they were airlifted to hospitals, Whitmore said. "The number of injured is hard to estimate at this point," Villaraigosa said. "We know that at least dozens have been injured ... maybe hundreds."Soon after the collision, dozens of injured passengers lay on blankets on both sides of the track. Passersby tried to free some passengers before fire and rescue crews arrived. Nine helicopters ferried the injured to hospitals.