Authorities in Loudoun County, Virginia, have released more details about a massive house explosion and fire in Sterling last week that killed one volunteer firefighter and injured more than a dozen other people.

In a news release Friday, the Loudoun County Fire and Rescue’s Fire Marshal’s Office said preliminary findings from the ongoing investigation into the origin and cause of the blast indicate it was the result of a leak in a 500-gallon underground propane tank, which was set off by an unknown ignition source.

Authorities said Friday they have wrapped up the on-site investigation in the charred ruins of the home on Silver Ridge Drive in Sterling. However, calling it “an extremely complex” investigation, the fire marshal said the incident will remain under investigation until further notice.

Volunteer firefighter Trevor Brown was killed in the blast. He had responded to the home, along with several other firefighters, for the report of a gas leak around 7:30 p.m. on Feb. 16.

The home exploded while Brown and other firefighters were inside.

Brown, 45, a father of three, had been with the Sterling Volunteer Fire Company since 2016.

Brown’s funeral is set for Monday, March 4, at Cornerstone Chapel in Leesburg, according to arrangements released by the county.

All told, 14 other people were hurt, including 11 firefighters. One firefighter remains hospitalized, in stable condition, at MedStar Washington Hospital Center’s Burn Center, according to an update from the county Friday.

The fire department said initial property damage is estimated at $2.5 million. In addition to the home that was destroyed, the blast caused damage to six additional residential structures. Three of those homes have been deemed unsafe to live in.