A man was found guilty of second-degree murder on Wednesday for the death in 2017 of a worker he had hired to dig tunnels for a secret nuclear bunker under his house in Maryland.

After more than a day of deliberation, a jury in Montgomery County found that the man, Daniel L. Beckwitt, 27, was responsible for the death of the worker, Askia Khafra, 21, who had been carving out hundreds of feet of passageways under Mr. Beckwitt’s home in Bethesda, Md., northwest of Washington.

A fire broke out during the work, and when firefighters arrived, they discovered Mr. Khafra’s “naked, charred body” in the basement, and a hole in the floor that dropped about 20 feet down and fanned out into tunnels spanning about 200 feet underground, according to court documents. The state medical examiner determined that the cause of death was smoke inhalation and thermal injuries.