SAN FRANCISCO (AP) ? Authorities are investigating mechanical and human errors as possible causes of a collision between two San Francisco light-rail trains that has left several dozen people injured.
Municipal Railway spokesman Judson True said the transit agency will conduct a speedy investigation and get to the bottom of the crash so that such an accident does not happen again.
"We take this incredibly seriously," he added.
Officials said 48 people were taken to hospitals ? four with what appeared to be severe injuries ? when one train struck the end of another at the boarding platform of the West Portal Station on Saturday afternoon.
"This is probably one of the largest multiple-casualty incidents in recent years (in San Francisco)," said Pat Gardner, a deputy chief with the San Francisco Fire Department.
Witnesses said a westbound train barreled into the other train as it emerged from a tunnel connecting downtown San Francisco to the city's western neighborhoods.
The front of the westboundtrain was smashed, while the other train suffered less damage. The operator of the westbound train was among the four with serious injuries. Officials said all the injured passengers were conscious and about half sustained moderate injuries.
The cause of the crash was under investigation, and True said investigators would look at "mechanical and human issues."
Shin San, 15, said her sister, Celene, was on the westbound train when it hit the other train and told her that she "heard a boom. She saw glass windows shattered and a guy got his ear cut."
Shin said her sister hit her head but did not suffer serious injuries.
Witnesses said more than a dozen people sat on benches along the boarding platform after the crash, some of them holding bloodied heads. Most of the passengers on the trains, which bustle with shoppers on Saturday afternoons, were adults.
Rescue workers set up a triage system to isolate the most severely injured, bandaging their heads and immobilizing their necks on stretchers before they were carted to waiting rescue vehicles.
"We thought a bomb went off," said Mike Burke, a San Francisco banker who lives near the crash site. He was walking past the station with his wife, Linda, after they went to the movies nearby.
"Lots of people (in the trains) were still sitting in their seats with their heads thrown back, stunned," Linda Burke said, adding that she saw people on the platform crying.
Dan Dudem, an unemployed mechanic, said he had just parked his motorcycle around the corner from the station when he heard the crash, and buildings in San Francisco's vibrant West Portal shopping district shook.
Saturday's crash was at least the third major transit accident in the United States since May.
Nine people were killed and more than 70 injured June 22 when a Metro train slammed into a stopped train on the tracks in Washington, D.C. The cause has not been determined but investigators say equipment that is supposed to detect stopped trains failed periodically in the days leading up to the crash.