Just outside the L'Enfant Plaza Metro station still sits the train where riders were trapped in a tunnel as it filled with smoke. Metro plans to remove the train Tuesday night and begin to repair the track as federal investigators search for answers.
The National Transportation Safety Board finished its work on scene early Tuesday morning, but the investigation won't likely be complete for six months to a year.
On Tuesday, riders returned to the station, but worries persist about the deadly incident and whether Metro is safe.
Investigators are focused on what caused an electrical arcing event in the rail line's power cables, what is known as the third rail.
FOX 5 has learned there may have been warning signs before this happened about smoke and fires that raised serious concerns.
"It shouldn't be like this," said Christine Kidd, who was riding Metro at L'Enfant Plaza with her young children. "This is the District of Columbia. Everything should be fixed. This is where the President lives."
Investigators with the NTSB worked into the early morning hours inside the tunnel where that Yellow line train stopped. It is still unclear if the train lost power or if the operator stopped because of the smoke ahead.
About 1,100 feet in front of the train, the NTSB found arcing in the electrified third rail which powers the cars. Investigators also found between a half inch to an inch of water in some places. That can pose a problem if it reaches the electric cables.
"It's a wet environment in many of these tunnels, and at this location, there is water," said NTSB railroad accident investigator Mike Flanigon.
Metro's tunnels are prone to leaks which are known to cause arcing insulators, smoke and sometimes fires. The transit agency reported 354 water leaks in the first quarter this fiscal year and anticipated 2,150 leaks, according to the most recent published reports.
"In certain cases, that arc can start sort of feeding on itself and it actually generates gases that are more conductive," Flanigon said.
Early last year, Metro reported an increase in smoke and fire incidents on the rail line. The problem was so concerning, according to minutes from the Tri-State Oversight Committee which oversees the transit agency, TOC inquired in May whether the uptick was "indicative of a more serious problem."
All of this will all be part of the NTSB investigation. Metro is cooperating, but has deferred all questions to the NTSB.
In a statement, board chair Tom Downs said, "once the cause of this incident is understood, we are prepared to take the actions needed to prevent this from happening again."
The woman who died has been identified as 61-year-old Carol Inman Glover of Alexandria, Va.
According to Metro, there were seven patients remaining Tuesday afternoon at George Washington University Hospital. There were two patients still at MedStar Washington Hospital Center Tuesday night. All patients at Howard University Hospital have been treated and released.
Despite the death and number of injuries, many Metro riders were undeterred even though safety is not far from their minds.
"It didn't affect my decision or my commute today," said Metro rider Anna Ragni.
At L'Enfant Plaza, the midday ridership appeared to be normal, with crowds forming on the platform waiting for trains. Additional Blue line trains are compensating for the Yellow line headed south, and to Largo with free shuttles available to the Pentagon.
Tom Davis, a rider who was at the station when the incident happened Monday, was not concerned, saying that "things happen" and safety is no bigger concern today than usual.
"Safety is a constant issue," Davis said. "It's an older system. It's aging. They should probably be more ahead of the curve getting things fixed."
The NTSB is also working with the Federal Transit Administration and TOC to help with the investigation.
The tracks were returned to Metro's control. The transit agency has not said when it anticipates those repairs will be done and service on the Yellow line returned to normal.
Statement from Metro Board Chair Tom Downs to Metro customers:
"On behalf of the Board of Directors and all Metro employees, I offer my deepest condolences to the family of the passenger who died yesterday following the incident on the Yellow Line. To those who were injured or frightened, and to the thousands who have been inconvenienced by this major service disruption, I offer a heartfelt apology. Please also know that Metro is working to restore full service as soon as possible.
"Metro is actively cooperating with the National Transportation Safety Board investigation that is now underway. This will be a thorough process that often takes time, and we understand that passengers want answers quickly. Please know that once the cause of this incident is understood, we are prepared to take the actions needed to prevent this from happening again. The safety of each and every Metro rider and employee remains our absolute highest priority."
Tri-State Oversight Minutes raising concerns about fire:
Metro Report on increase in smoke and fires on Metrorail:
Metro Report which details number of leaks in FY2015: