A school bus drives by the remains of the Flower Branch Apartments in Silver Spring, Md., soon after the explosion and fire that killed seven there in August 2016. (Jabin Botsford/The Washington Post)

Nearly three years after an explosion destroyed two apartment buildings and killed seven people in Silver Spring, the National Transportation Safety Board pointed to failed Washington Gas equipment on Tuesday as responsible for the tragedy.

The gas company immediately pushed back on that conclusion, an indication that blame will ultimately be decided through lawsuits filed by tenants and relatives of the dead against Washington Gas and the landlord, Kay Management.

The NTSB said a failed gas regulator and a disconnected vent line probably allowed gas to build up “to an explosive level” inside a basement meter room at the Flower Branch apartments, a mostly low-income complex just outside Washington.

Eventually, the gas reached “an ignition source” that sparked the blast, according to the agency, which in addition to investigating civil aviation accidents in the United States probes significant railroad, highway and marine accidents, as well as those involving pipelines.

The regulator and vent were owned and operated by Washington Gas and were the utility’s responsibility to maintain, NTSB investigator Rachael Gunaratnam said during an agency board meeting.

But Gunaratnam said other breakdowns contributed to the dramatic explosion, which killed five adults and two small children, most of them immigrants.


Stuffed toys attached to the fence at the sitet of the explosion at the Flower Branch Apartment complex, where five adults and two children died in August 2016. (Michael S. Williamson/The Washington Post)

Despite numerous instances of people smelling gas in the weeks before the explosion, neither Kay Management, which runs the Flower Branch Apartments, nor firefighters notified the gas company, she said.

Kay Management changed the lock to the meter room without making a new key available to the fire department as required by law, Gunaratnam said. As a result, firefighters responding to a call about the smell of gas two weeks before the explosion were unable to get into the meter room. After prying the door partially open and not detecting gas, she said, firefighters left.

“Six times in the weeks and months preceding the accident, residents reported a natural gas smell to Kay Management,” NTSB Chairman Robert L. Sumwalt said during Tuesday’s meeting. “In each case, maintenance staff reported that they did not detect gas or attributed the smell to the painting of apartments.”

Washington Gas chief executive Adrian Chapman said in a statement Tuesday that while company officials have “great respect for the NTSB and we know they worked diligently,” the company disagreed with the findings.

The company does not think the evidence showed a failure of its equipment, Chapman said. “We also do not believe the NTSB sufficiently investigated the other potential causes of the explosion.”

Clark Melillo, president of Kay Apartment Communities, said in a statement that he accepted the NTSB’s conclusion — “that there was a gas regulator failure and a disconnected vent pipe — equipment not owned or maintained by Flower Branch Apartments.”

“While the NTSB’s conclusions and recommendations cannot make up for the loss of life,” Melillo said, “we hope others will learn from this tragic incident and take steps to prevent it from ever happening again.”

The statement did not address the NTSB’s allegations that his company failed to provide fire responders a key to the meter room or notify Washington Gas when residents thought they smelled gas.

In an undated report contained in materials made public Tuesday by the NTSB, explosives investigator Lt. William Olin of Montgomery County Fire and Rescue Service praised the NTSB’s “professionalism, their methodical and scientific approach,” but took aim at Washington Gas, saying the utility was defensive during the fire department’s investigation.

“Washington Gas treated meetings and interviews more like a court room cross examination than a joint investigation geared at finding the cause of a tragic accident,” Olin wrote.

His report was highlighted by NTSB board member Jennifer Homendy. “I strongly suggest that Washington Gas refocus its attention on actions they could have taken to prevent this accident from occurring, rather than spend time telling us how to conduct our safety investigation,” Homendy said.

The NTSB made recommendations Tuesday aimed at preventing similar explosions. They include requiring that all new gas regulators be installed outside occupied structures, so that any leaking gas can escape into the atmosphere. The agency also recommended revising national protocols to direct emergency dispatchers to notify the gas company directly when any report about gas odor is received.

Lawsuits over the Aug. 10, 2016, explosion at Flower Branch Apartments — which injured more than 30 people and displaced more than 100 — have pitted dozens of poor, mostly Spanish-speaking residents against Kay Management and Washington Gas.

The litigation stalled while the NTSB finished its investigation, a delay that has frustrated victims and local officials and that the agency attributed to staffing problems — including the sudden retirement last year of the investigator in charge — and the need to be thorough.

Any NTSB conclusion about the explosion’s cause would be restricted by law from use as evidence in court, lawyers say. But the prolonged investigation has hindered the legal process in other ways.

For one thing, the NTSB has custody of physical evidence — such as burned wreckage of gas lines and meters — that attorneys in the lawsuits want their own experts to examine.

Victims of the explosion have had to wait. Some lost family members, some were injured, others lost possessions. Many suffered mental and emotional trauma.

For them, the findings released Tuesday were one more step on a long road that leads to the courtroom, said Ana Martinez, an organizer for the immigrant advocacy group Casa, which has been providing support for victims of the blast.

“We want to make sure that what happened at Flower Branch doesn’t happen again,” she said.