In the aftermath of Tuesday's debacle on the Blue Line, Metro announced it will inspect the brakes on some of its rail cars.
Already, 16 rail cars have been taken out of service as part of the inspection, officials said.
Hundreds of people were stranded Tuesday morning when a piece of brake mechanism, called a friction ring, fell off a 5000-series rail car between the L'Enfant Plaza and Smithsonian stations.
The agency believes the ring landed between the tracks and the electrified third rail and was hit by two Orange Line trains.
Metro rider Vann-Di Galloway was on the platform when the ring came off and says he told two Metro employees on the next train, who called it in. However, the train left anyway.
"As the train was leaving there was a scrunching sound," said Galloway. "It sounded like the train hit something metallic. As the train accelerated, there was an explosion. Very loud bang. Underneath that car between the tracks, I could see lights like licks of flames like a fire ball. As the train left the station, it left a trail of very acrid smoke, black smoke."
Justin Pearson, a Metro rider, saw the conversation between Galloway and the Metro employees.
"[The Metro employees] looked at [Galloway] like he was crazy," Pearson said. "We began to drive like a minute down the track then you hear a boom the train vibrates then you hear a boom boom."
A Metro spokesman acknowledged that the agency was aware of the reports and said they will be "interviewing the train operators."
The investigation has already indicated the agency needs to improve its communications with customers and address issues with radio service in the tunnels.
Service was brought to a standstill for several hours in one of the busiest corridors in the Metro system - between Metro Center and Federal Center SW.
Metro says the friction ring dislodged from a train car and landed on the track at about 9:40 a.m. The ring struck the third rail, causing sparks and smoke in the train tunnel.
"It sounded like the train hit something metallic," passenger Vann-Di Galloway said. "As the train accelerated there was...a very loud bang."
On Wednesday, Metro officials said that the loss of the friction ring may have resulted in the failure of a hub, which is the portion of the brake assembly that holds it in place.
Metro has identified 34 hubs in 16 similar rail cars, which have been removed from service.
Hundreds rescued from stalled train
About 300 people had to be rescued from a stalled train, but some riders said they were upset by a lack of communication from WMATA workers and officials. Riders waited for about three hours to be evacuated.
"They simply said, 'Ha, we are experiencing difficulty. Thank you for riding Metro. We thank you for your patience.' At that point, the whole car just went up. They were livid," passenger Josie Brown said.
Passengers did commend D.C. firefighters and first responders for their work to help evacuate the stuck train. But some say they heard nothing at all from Metro for about an hour, and at that point, there were simply notified of technical difficulties.
Regular service did not resume until about 2:30 p.m. No serious injuries were reported as a result of what Metro says was an isolated incident.
Metro targets two improvement areas
The outcry over the perceived lack of response from WMATA employees and officials have prompted the agency to identify two areas of improvement.
Metro says that they will look at how employees communicate with customers both aboard stranded trains and at stations where stopped trains are headed.
WMATA also will look to improve radio communications and improve signal boosting in areas that have traditionally spotty communication service.