WASHINGTON – The National Transportation Safety Board was investigating what caused a subway train to derail near downtown Washington, sending 20 people to the hospital.
Witnesses said people started to panic Sunday when the six-car train began shaking, and some passengers began running to the back of the train as it approached the underground Mount Vernon Square station.
"I was in a cab that actually shattered -- the front part of it -- those windows in between the two cars," rider Lauren Sprigg said.
The accident on the city's Metro happened at about 3:45 p.m., Metro spokeswoman Cathy Asato said. There were about 150 people on the train.
One person had a serious but not life-threatening injury, Asato said. The other injuries were mostly "bumps and bruises," and one of those with minor injuries was pregnant.
Service on the two lines was halted in both directions around the station, and Asato said a shuttle bus would take passengers around the accident scene.
After NTSB investigators examined the scene, Metro workers began removing the train, but they didn't know how long it would take. Metro spokeswoman Lisa Farbstein said it was unclear whether the station would be open in time for the morning rush hour.
"Right now the focus of the investigation is the rail and the car," said Kitty Higgins, a member of the NTSB. "We will be investigating the track, both at the site of the derailment but also for several hundred feet on either side of the derailment to understand what condition the track was in."
The incident follows two accidents in 2006 in which a total of three Metro track workers were struck and killed. Federal investigators at the time questioned whether the train operators were following safety procedures.
Higgins said the number of recent accidents was "cause for concern."
"This is an important system," Higgins said. "It's our nation's capital. We want to make sure it's as safe as possible."
Part of the six-car train had pulled into the station when the fifth car left the track and hit the tunnel wall, Asato said. All the train cars remained upright.
Glass and metal debris was strewn through the tunnel, and the fifth car of the train had significant damage, Farbstein said. Part of the car was ripped apart, Higgins said.
"When we were down in the tunnel, we could see the point at which it left the track," Higgins said.
The concrete tunnel wall also appeared to be damaged, though the extent of the damage was not known. It also was not immediately clear whether the track itself was damaged.
The train operator was undergoing routine drug and alcohol tests, Asato said. The woman had been operating Metro trains since 2000. NTSB investigators planned to interview her Monday, Higgins said.
Investigators are also planning to examine information from the train's data recorders to determine details such as how fast the train was going and when the brakes were applied.