WASHINGTON (CNN) -- The head of Washington's mass transit system praised as a "hero" the driver who was killed in Monday's crash when her train struck another that was parked on the tracks.
Emergency personnel investigate the scene of a Metro subway train collision in Washington.
"She saved lives," said Metro General Manager John Catoe at a memorial service Friday for Jeanice McMillan.
McMillan was one of nine people killed when her train, under automatic computer control, apparently failed to register a signal and avoid a collision with a train that had stopped near a curve between two stations.
Accident investigators testing the control circuitry in the days after the collision found problems along the line near the crash scene. The same circuit had been worked on just weeks before the crash, according to repair records.
When a test train this week was parked in the same location, the control circuitry did not signal that it was there.
The National Transportation Safety Board also found evidence on the brake discs and the rails leading up to the crash scene suggesting McMillan may have applied the brakes manually in the moments before impact.
At Friday's memorial service, Catoe told friends and family members: "On Monday when we had this tragic loss, she was there not just doing her job, she took an act that I believe, in my judgment, ultimately will determine that she saved lives."
"She did not back away from her opportunity," Catoe said, as those gathered began to applaud. The congregation eventually stood and continued applauding, and Catoe stood by to let their response continue, delaying his remarks for nearly a minute.
"We will honor her at Metro, as the Metro hero," Catoe said, as the applause began again, "she will always be in our hearts from that perspective."
A young man then stepped up to address the service. He seemed nervous but determined to get his message across. It was the woman's son, Marquel, who described simple evenings at home and in touch.
" 'Marquel, come here!' he said, in a parental tone of voice, as the congregation laughed softly, "I'm just gonna miss that, just hearing her call my name."
Thanking those who have reached out to him since his loss, he said "If it wasn't for y'all, I don't, I don't know, I just ..." . He sighed and his voice trailed off.
But the congregation cheered and applauded to encourage him to go on, and he said his mother made sure his two uncles were in his life, "and now I know why. When everything's like this, happening, we already have a close bond."
The two men then helped Marquel back to his seat.
Friday, accident investigators continued collecting data, reviewing repair records and examining pieces of wreckage that could shed light on the cause of the crash.
NTSB Board Member Deborah Hersman on Wednesday disclosed that there were "anomalies" in the control circuitry, but told reporters there would be no conclusions until the probe is complete.