Four people were killed instantly when a single-engine plane crashed in flames in a heavily wooded ravine in Prince William County shortly after takeoff yesterday from Woodbridge Airport. A fifth person died later.

Two of the victims were identified late last night by Virginia State Police as Catherine Rita Hall, 33, of 5811 Edsall Rd., Alexandria, and her 6-month-old son, Theodore Ewing Hall.

The other three were not immediately identified. The victim who was alive when pulled from the wreckage, an adult male, died at the Washington Hospital Center.

Investigators from the Federal Aviation Administration and the National Transportation Safety Board were on the scene, but the cause of the 12:40 p.m. crash and the pilot's name and destination were not immediately known.

Airport personnel said they believed the plane was bound for its home base in New Jersey after a one-day visit.

They said the plane was registered in New Jersey and had been fully fueled shortly before takeoff.

The plane, identified by the FAA as a Grumman American Aero Commander, took off on the airport's single runway and climbed quickly with its 200-horsepower engine roaring in what sounded like a normal takeoff, according to Al Jones, a flight instructor who watched the plane leave the airport where about 150 small planes are based.

But as soon as the four-seater plane cleared the trees about 100 yards from the runway, it banked suddenly to the left and veered downward at a sharp angle, Jones said.

"I saw it disappear into the trees. I didn't hear the engine cut out. The engine sounded great," he said.

Virginia State Police said they believed the engine stalled at an altitude of about 50 feet.

The plane fell through the trees at a steep angle, searing and shearing off treetops as it plunged into a shallow ravine west of the airport.

FAA investigators said the plane flipped onto its back as it fell and was incinerated, with the only remaining identifiable parts being pieces of the tail, frame, engine and seats.

Prince William fire crews used portable pumps after they made their way into the woods and extinguished the blaze. Fire and rescue crews took the injured man by a four-wheel-drive ambulance to a clearing where he could be picked up by a Fairfax County police helicopter.