Investigators in the U.S. capital were focusing Tuesday on why a computerized system apparently failed to stop a train from crashing head-on into another, even though the emergency brake was applied.

The train had been set on automatic mode, which means it was mainly under the control of a computer. That left the operator responsible for opening and the closing the doors, and taking over in an emergency.

At least nine people died in the Washington, D.C., crash, and more than 70 people were injured.

Train operator McMillan was two years on the job driving a bus, but only a few weeks as a train operator. It appears that she tried to turn on the emergency brake, but it's unclear whether the brake was actually engaged.

Investigators also said the train was part of an aging fleet that federal authorities had recommended be phased out or retrofitted because of safety concerns.

The aging train plowed into another train stopped on the tracks during rush hour on Monday as it reportedly waited for instructions to proceed.

The accident is the deadliest in the Metro train transit system's history.

The National Transportation Safety Board is heading the investigation. Spokesperson Debbie Hersman said the Metrorail transit system "was not able" to replace the older train despite warnings dating back to 2006.

Metrorail officials blame money. The subway system has 296 rail cars that were built more than 30 years ago, and it hasn't had enough money to cover the estimated US$888 million needed to replace them, spokesperson Candace Smith said.

Investigators were expected to recover recorders from the train that was stuck, which would have offered valuable information about what happened.

However, because the train that triggered the crash was so old, it was not equipped with the recorders.

It unclear whether age played a role in the rush-hour collision, however, investigators are looking at speed as a factor. They are trying to determine the speed of the train at the time of the crash.

Death toll

Speaking at a press conference Tuesday afternoon, Mayor Adrian Fenty confirmed the identity of some victims.

Among them were train operator Jeanice McMillan, 42, of Springfield; Mary Doolittle, 59, of northwest Washington; Ana Fernandez, 40, of Hyattsville, Md.; Dennis Hawkins, 64, of southeast Washington and Lavonda King, 23, of northeast D.C.

It was not immediately clear whether the passengers killed were on the train that was moving or the one that was stopped awaiting the train ahead of it to clear a station.

"It happened so fast, I flew out of the seat and hit my head," said passenger Jodie Wickett.

"The people that were hurt, the ones that could speak, were calling back as we called out to them. Lots of people were upset and crying."

Passenger Maya Maroto, 31, said, "We were going full speed -- I didn't hear any braking. Everything was just going normally. Then there was a very loud impact. We all fell out of our seats. Then the train filled up with smoke. I was coughing."

The Metrorail board has set up an emergency relief fund of 250,000 to be distributed among the victims and are seeking to replace the old models of trains.

Meanwhile, rescue crews have been using heavy equipment to cut through the mangled train cars.

The crash took place on a Metro route that shuttles tens of thousands of commuters each day between the Maryland suburbs and the city.

There has not been a Washington Metro collision fatality since January 1982.

With files from The Associated Press