Circuits on all Metro train tracks throughout the Washington, D.C., system will now be inspected after investigators found an "anomaly" in one of the circuits close to the site of a crash that killed nine riders.
"We do not know if the circuits had anything to do with this accident, but we won't just sit back and wait for someone to tell us," John Catoe, general manager, said today at a meeting with board members, according to a statement from Washington Metro Area Transit Authority. "We're going to be proactive and get out there to test all of them."
About 3,000 circuits will be get a closer look during the next few weeks, Catoe said.
On Thursday, investigators were also interviewing the operator of the train that was violently struck by another train Monday evening. The train operator was released from the hospital Wednesday and will be questioned by teams trying to learn more about the accident.
Investigators Examine 'Anomaly' in Key Track Circuit
Investigators on the train track Wednesday found that a key circuit monitoring 740 feet of the track near Monday's derailment may not have been operating as it should have. The find raised the possibility that the Metro train that crashed into a stopped train may not have gotten the indication to slow down.
Investigators tested six circuits between the two stations where the crash occurred. Five of those performed as expected, according to National Transportation Safety Board investigator Deborah Hersman. But one circuit showed what Hersman described as an "anomaly."
The NTSB has now put a stand-in train on the track to conduct additional tests.
Circuits along Metro tracks are a critical part of the automatic train control system. They let trains know how fast to go and provide them with information about whether there's another train up ahead. The computerized system is designed to keep trains from coming within 1,200 feet of each other.
Investigators have determined that the train was indeed running on automatic mode when it crashed and are investigating why built-in safety features of that system did not prevent the accident.
Since the crash, Metro operators have been running trains manually.
"What causes us concern the most is the fact that this was not supposed to happen," Jackie Jeter, president of Amalgamated Transit Union Local 689 said Tuesday. "There are safety mechanisms that are on place on the trains to prevent this type of accident. And, for me, as president of the union and as a train operator, I have to wonder why didn't those safety mechanisms kick in and prevent it."
Train recorders will provide insight into what happened as the information is evaluated over the next few days, former National Transportation Safety Board investigator Barry Sweedler said. The train that was hit had several recorders on it, but the one that collided into it didn't have any.
NTSB Had Warned Metro Trains Could Be Dangerous
Hersman of the NTSB said Wednesday it appeared the train operator braked 300 to 400 feet prior to the crash site. NTSB investigators at the scene found "bluing" on the track, indicating emergency braking. They don't yet know how fast the train was going when it collided with the other, but said they will, at some point, be able to ascertain that information.
Also Wednesday, the NTSB said found no indications in train records of overdue maintenance despite earlier reports that the brakes on the train may have been behind schedule for a check-up. The train was last examined in late May.
"We do have an independent train system ... [but] let's not try and disperse the blame. Let's put it on the decision makers and the leaders," Fenty said on "Good Morning America."
Fenty said that while replacing or retrofitting the cars "to make them more crash resistant" would have been expensive, "lives are more important than finances."
Despite the two NTSB warnings, transit officials had refused an upgrade because it would be expensive and complicated.
"We have planned for the replacement of these railcars and are in pursuit of the funding to make that happen," Catoe said Thursday.
In 1996, a Metro train of the same series failed to stop and crashed into an unoccupied train in what the NTSB called "catastrophic failure." After the crash the NTSB recommended a comprehensive evaluation of the cars. In 2002, D.C. Metro declined to make any changes. A similar crash took place in 2004, and the NTSB reiterated its warnings.
"In 2006 [the NTSB] asked them to look at old cars," Hersman told "GMA." "They did not retrofit the cars to the standard the safety board was looking for."
Hersman emphasized that the NTSB's role was to make recommendations, and that it was up to local and federal authorities to decide whether to act based on those recommendations.
Faces of the Dead: Family Members, Servicemen
Train operator Jeanice McMillan, 42, was among those killed in Monday's crash. She was running the train that struck the one in front it stopped on the tracks.
Other victims of the accident ran the gamut from a young mother of two to a military officer.
The military officer killed in the crash was Major General David F. Wherley Jr., who died alongside his wife, Ann. Both were 62. Wherley, a career military man had recently retired as the head of the D.C. National Guard. It was his order that scrambled jets over Washington, D.C., Sept. 11, 2001.
"He was as fine a public servant, as dedicated to the United States of America as anyone I have ever met," Fenty said.
Also on the train was 40-year-old Ana Fernandez, killed while on her way to a nighttime cleaning job. She left behind six children.
Passenger Dennis Hawkins, a 64-year-old retired teacher, died while on his way to teach a Bible class.
And Lavonda King, just 23 years old, was killed as she took the train to pick up her two sons from daycare. Her mother said King had dreamed of a better life for her boys and had recently signed the paperwork to open up a beauty salon.
McMillan, who had been on the job for four months, was also a mother. The son she raised by herself had started college in the fall. Her family said she took pride in her work on the train and ironed her uniform nightly.
"She loved the train. She would talk about what she did at work, or how this works," said her brother, Vernand McMillan.
ABC News' Lee Ferran, Sarah Netter and Jay Shaylor contributed to this report.