Work on Metro’s busy Red Line turned deadly this weekend after a contractor was critically injured in a Metro tunnel explosion.

The contractor was transported to Howard University Hospital where he later died , Metro officials said. Two Metro employees were in stable condition and suffered back-related injuries that Metro said are “serious but considered non-life-threatening.” One of the workers was being treated at MedStar and the other at Howard.

Metro officials identified the contractor as Harold Ingram, 41.

The accident happened shortly after midnight Sunday in the tunnel about 400 feet from the Union Station platform in the direction of Judiciary Square. There was an explosion and then a fire in the tunnel.

A portion of the Red Line in the downtown core had already been shut down to riders since Friday night so crews could put in new track in the area as part of Metro’s major system rebuilding project.

Fatal accident delays repairs on red line

While track work in that area has been suspended due to the accident, Metro said it would continue to provide free shuttle buses between Dupont Circle and NoMa-Gallaudet stations until rail service is restored. Normal service will resume before the Monday morning commute.

Metro officials said they were conducting an investigation into the cause of the accident and had notified the Tri-State Oversight Committee, which helps in overseeing the transit agency, and the National Transportation Safety Board.

“Our first order of business after attending to the injured is to prevent anyone else from being hurt,” said Chief Safety Officer James Dougherty. “We also need to ensure we have the safest possible working conditions going forward, which means learning lessons from the investigation of this accident.”

Initial reports show leaking hydraulic fluid from an underground vehicle apparently was ignited by welding equipment, causing an explosion and fire. The injured workers were helping install a heavy, roughly 40-foot-long piece of new rail in the closed-off area.

About 100 Metro employees and contractors had been working in the closed-off section on six different projects, using about a dozen heavy pieces of machinery.

Dan Stessel, a Metro spokesman, said Sunday morning that the two Metro employees suffered injuries that were “consistent with making contact with a piece of rail.”

“The primary cause of their injuries was not due to fire,” he said. “They’re not burns.”

Stessel also said “the fire was not the cause of injury or fatality based on what we know right now. How that piece of rail came into contact with the workers is under investigation.”

Workers in the tunnel put out the fire with an extinguisher before D.C. Fire personnel arrived on the scene, according to Metro officials and workers on the scene.

The vehicle that may have been leaking hydraulic fluid belonged to Holland Co. of Crete, Ill., and Metro had a contract with the company for welding services. Heather Stone, a spokesman for Holland Co., said the company does welding services for Metro. She confirmed that the contract worker who was killed in the incident worked for the company and said Holland was sending safety and operational personnel to the scene to investigate. She said she could not confirm initial reports that a piece of equipment that belonged to Holland Co. was leaking hydraulic fluid.

Much of the equipment used in rebuilding of Metro’s track contains hydraulic fluid. Leaking fluid has caused problems for riders at least twice this year.

In July, leaking fluid caused a train to become disabled near Clarendon, snarling the evening commute for thousands of riders. In March, a leak from a “prime mover” near Reagan National Airport sparked lengthy single-tracking on the Blue and Yellow lines. The leak came from a “prime mover,” which is used to shuttle heavy equipment through the rail system, as it was being moved off the rail lines.

Metro’s employee safety record had been under particularly close scrutiny a few years ago when seven workers were killed in a series of incidents between 2005 and 2010. In one incident in January 2010, two Metro track workers were struck and killed by a piece of rail equipment near the Rockville Metro stop.

Sunday’s incident comes as Metro has been doing two years of aggressive track work nearly every weekend. Until the early Sunday morning incident, it appeared that this weekend’s reconstruction had gone relatively smoothly, despite some riders’ surprise at the closure of five key stations, from Farragut North to Union Station. Riders were able to use the Blue and Orange lines at Metro Center and the Yellow and Green lines at Gallery Place.

The shutdown affected nearly one-quarter of passengers who travel over the weekend. Many riders whose trips took them through the downtown area had to get off the train, take a free Metrobus around the closed area and get back on the subway to continue their trip.

Metro staffers were at stations to direct riders to shuttle buses, but some riders said it wasn’t always clear which buses were going where or if drivers borrowed from suburban routes knew their way around the city.

On Sunday morning, few Metro workers who were helping direct passengers or riders trying to get around knew of the tunnel incident. Most riders were simply focused on how to get off the rail and find a shuttle bus to get them to their destination.

Bruce Wortham of Anacostia said Sunday morning the weekend shutdown took him longer to get home from his overnight job at the Giant grocery store at Van Ness.

“I didn’t know this was going on when I went in Saturday and it made me an hour late getting into my job and now it is adding 30 minutes to me getting home,” he said as he got off the train at Dupont Circle and looked for a shuttle bus to Gallery Place. “It’s a pain.”

For other riders Sunday morning, getting around the closed off stations on the Red Line wasn’t an issue.

“It was easy for me,” said Angelica Riepe, of Chicago, in Washington for a professional conference.

“I figured Sunday morning would be the perfect time to try it and it wasn’t bad at all,” said Riepe, who boarded the shuttle bus from Dupont to Farragut North. “I was glad they had workers giving direction.”

But other riders were annoyed Saturday when they found that some escalators were out of service at Metro Center. At the top of one, people with luggage and carrying babies were met by a Metro staffer saying, “I’m sorry, I’m sorry,” and directing them to a nearby shuttle bus.

Although the closures frustrated some riders, Metro officials said the shutdowns give crews more uninterrupted time to work on a heavily-traveled segment of the aging system. Nearly every weekend for the past two years, the transit agency has run shuttle buses in some part of the system because of shutdowns.

The weekend closures come at a time when Metro is already seeing a dip in ridership, especially last week, when it dropped 20 percent because of the federal furloughs.

By midday Saturday, Metro officials said operations during the shutdown were smooth. The agency had carried 11,232 passengers on 147 shuttle bus runs.

Staff writers Martin Weil and Mark Berman contributed to this report.