An engine housing from a Northwest Airlines DC10 fell off in a ball of fire and shower of sparks and then crashed into a yard in a Leesburg town house complex last night a few minutes after the jumbo jet took off from Dulles International Airport.

No injuries were reported on the ground or in the Seattle-bound plane, which returned safely to the airport, as emergency equipment lined the runway.

The three-engined transport took off about 6:05 p.m. from Dulles with 43 passengers on board, and had climbed to 7,000 feet when the pilot "felt the plane shudder a little bit, and decided something was wrong," a Federal Aviation Administration spokesman said.

After the plane returned to Dulles, the spokesman said, it was found that part of the cowling, or housing, of the number 3 engine, the one mounted under the plane's right wing, had apparently broken off.

The plane taxied to the boarding area and was reportedly parked there last night pending investigation of the incident. No cause was known immediately.

"There was a ball of fire and a huge shower of sparks," said Douglas Nicklow, who was driving north on Rte. 15 toward his Leesburg home when he saw the plane overhead shortly after 6 p.m. "It looked like fantastic 4th of July fireworks."

About the same time Mike Sherman, watching television in his Leesburg town house, heard what sounded "like two cars hitting each other."

He went outside to find the chunk of engine housing, about 10 feet in diameter and seven feet long, in his yard.

Although it cracked his sidewalk and gouged his lawn, Sherman said, the housing missed nearby powerlines, houses and parked cars. It was "very amazing," he said.

An engine tore off the left wing of a DC10 as it took off in Chicago in 1979, killing 273 persons. Subsequently, 137 of the planes operated by U.S. airlines were grounded for 38 days. Investigators later ruled that the accident was caused by a crack in a pylon that holds the engine to the wing and modifications to the pylons were ordered.