A natural gas explosion rocked a quiet Seat Pleasant neighborhood yesterday, obliterating one home and destroying most of another in a Booker Drive duplex. Three workmen and a woman resident were injured.

Betty Sue Parker of 924 Booker Dr. smelled gas in her home and rushed her five children across the street. As she returned to her front porch, the house exploded, leaving only the charred frame of the other half of the duplex standing.

Parker was badly shaken but not seriously injured and was released after being examined by a physician.

Prince George's fire officials and Parker's husband said three workmen were in the back yard of the home, where they were building an addition, when one of them drove a backhoe into the buried gas line.

The gas leaked into the house for about 10 minutes while a workman tried to shut off the line in the basement.

Fire officials surmised the gas was ignited by a spark or flame. Damage was estimated at $130,000.

Washington Hospital Center officials said Alfonzo Stevens, 35, was in serious condition in the burn unit with second-degree burns on his face and back and third-degree burns on his hands.

Prince George's Hospital officials said William Alston Sr., 43, and his son, William Jr., 18, both hit in the face by flying glass, were treated and released.

Derek Frisby, a neighbor, said he heard the explosion, rushed outside and ran to the house, where he found Parker on the porch in a daze. He carried her to safety.

Meanwhile, Daniel W. Anthong, another neighbor, came to the rescue of Edith Butler, who lived at 922 Booker Drive, the other part of the duplex.

Anthony's wife, Gladys, said she was talking on the telephone at the time of the explosion and was knocked off her chair onto the floor. She scrambled for the door, where she heard her husband shout, "The Parkers' house just blew up."

A neighbor standing outside as firemen hosed down the wreckage said it "looked like a bomb dropped on it."

Another neighbor, Alexis Adams, said: "All I thought to myself was, Oh no, here comes God."

All that was left of Parker's home was a large pile of smoking rubble, burned wood and bricks scattered over the fenced-in yard.

A piece of wrought-iron gate was catapulted into the second-floor window of a nearby house.

A small blue tent remained standing beside the charred ruins.