Officials work at the scene of a rush-hour collision between two Metro transit trains in northeast Washington, D.C., on Tuesday. (Charles Dharapak/Associated Press)

The emergency brake on the D.C. Metro train that rammed into another commuter train appeared to have been deployed and the train was in automatic mode at the time of the deadly crash, a federal investigator says.

National Transportation Safety Board official Debbie Hersman pointed out that during rush hour, the train operates in automatic mode.

Hersman said they found that the emergency brake was in a "depressed condition." She acknowledged that could have occurred because of the accident or during the removal operation.

However, she said the wheels were in a mode consistent with having the emergency brake applied.

A six-car commuter train rear-ended a stationary train on the Red line between the Takoma and Fort Totten stations at the peak of evening rush hour on Monday. The route, Metro's busiest, shuttles thousands of commuters each day between the city and the D.C. suburbs.

One of the two trains was stopped on the tracks near the Fort Totten station, waiting for a train to clear the station ahead, when the other train plowed into it from behind.

Hersman also told reporters that the operator of the striking train had roughly three months of experience as a train operator.

She said the operator, identified as Jeanice McMillan who was among the nine people killed, had been hired in January 2007 as a bus driver.

Hersman said McMillan started training as a train operator in January 2009, completed the training and began working as a train operator in March.

Hersman said the investigation will also look into McMillan's 72-hour history, to look at her work/rest schedule.

"Fatigue is a big issue in transportation accidents. What we want to check is their duty time and their rest time and see what they are doing in their off-duty hours," Hersman said.

Toxicology samples have been taken and they will be looking into whether McMillan was using a cellphone or texting during the accident.

According to one of the passengers on the striking train, an announcement was made that there was a stopped train ahead and their train had stopped. The train then started again and the collision occurred.

Earlier, Hersman had said investigation into the deadly crash indicated that an advisory had been issued to phase out the aging model that triggered the crash, according to federal investigators.

Hersman said the train was part of an aging fleet that federal regulators had recommended in 2006 to be phased out or retrofitted.

Neither was done, she said, which the NTSB considered "unacceptable."

Washington Metropolitan Area Transit Authority officials planned to replace the old trains but were years away from them rolling on the tracks.

Investigators and officials look over the collision scene of two Metro transit trains on Tuesday. (Gerald Herbert/Associated Press)

Among the safety problems with the trains were concerns about them rolling back on their tracks and operators not being able to stop them, Hersman said.

Hersman said investigators expect to recover recorders from the train that was struck, providing information that might help determine why the crash occurred. However, the train that triggered the collision was part of an old fleet that was not equipped with the devices, she said.

The three-decade-old Metro system shuttles tourists and local commuters from Washington to Maryland and Virginia suburbs.

No immediate explanation has been cited for the possible cause of the accident.

The scene of the crash is still being scoured by fire and rescue officials, said fire Chief Dennis Rubin. Heavy equipment is being used to pull apart the train wreckage and to cut through it, he said.

Extra safety measures established

All of the system's trains are operating in manual mode until the cause of the crash is determined, and extra safety measures are being taken at stations, said Metro general manager John Catoe.

"We are committed to investigate this accident until we determine why this happened and what must be done to ensure it never happens again," Catoe said.

Fenty previously called the crash the deadliest accident in the history of the Metro system. The second deadliest incident on Washington's Metro system was a derailment on the Orange line between the Federal Triangle and Smithsonian stations that killed three people in January 1982.

The last major commuter crash in the United States was in September 2008 in Chatsworth, north of Los Angeles, when a commuter train collided with a freight train. Twenty-five people died and 134 were injured in that crash, the worst train crash in the U.S. in about 15 years. Investigators found that the engineer of the commuter train was sending text messages on his mobile phone prior to the crash.

With files from The Associated Press