Two District residents were killed last night when they were trapped in a Colmar Manor garage fire that Prince George's County authorities said was ignited by explosives they apparently were using to produce illegal fireworks.

Fire Department spokesman Tony DiStefano said the bodies of Richard Lee Thompson, 25, and Lillian Thompson, 56, both of 2015 First St. NW, were found in the rear of a deep brick garage at 3505 43rd Ave. that apparently was being used as a storehouse and laboratory for the manufacture of commercial fireworks.

DiStefano said a man was taken into custody for questioning in connection with the explosion.

He said the county bomb squad was called in to sift through the rubble and had found four or five bags of empty casings that are seven inches long and two inches in diameter comparable to those used in "a small stick of dynamite." DiStefano said the casings typically are used in the manufacture of fireworks. Manufacturing explosive devices without a license is illegal in Prince George's County.

Lawrence Dawsell, 74, who also lives at 3505 43d Ave., said the man being questioned by police early today and a 13-year-old boy, who was not identified, were also in the garage at the time of the explosion.

Dawsell said Lillian Thompson was Richard Thompson's aunt.

According to DiStefano, firefighters were called after someone saw smoke coming from the garage about 8:20 p.m. The explosion came with what some firefighters called stunning force as fire units arrived.

The blast blew a hole in the garage roof and pushed its walls out. The fire was extinguished in five minutes, DiStefano said.

Several neighbors said they felt a shudder from the blast, and some said flames reached 40 feet into the air.

"It sounded like a bomb going off," said Robert Joyner, 53, who at the time of the explosion was standing on the front porch of his home across the street at 3504 43rd Ave. "The blast blew me backwards."

His nephew, Charles Joyner, 22, said the explosion was "like a wave of air . . . . You could hear the glass shattering in the house" alongside the garage.

Robert Joyner, who has lived in the neighborhood for three years, said the house at 3505 seemed to be constantly full of people.