Military investigators are focusing on whether a malfunction or inadvertent pilot error caused a D.C. Air National Guard F-16 fighter jet to fire 27 rounds at a New Jersey middle school during nighttime target practice this month, the pilot's commanding general said yesterday.

Briefing Sen. Frank R. Lautenberg (D-N.J.) and reporters in Washington, Maj. Gen. David Wherley Jr. said he expected findings from accident and safety investigations into the Nov. 3 incident at Little Egg Harbor Intermediate School to be delivered within three weeks.

No one was injured in the incident, which occurred about 10:15 p.m. at the school, in a coastal township about 20 miles north of Atlantic City.

The pilot, a major with the 113th Fighter Wing, known as the "Capitol Guardians" and based at Andrews Air Force Base, has been suspended from flying pending the outcome of the investigations.

The investigations will help determine whether administrative or criminal action is warranted, Wherley said, and whether training will resume at Warren Grove Gunnery Range. Training there was suspended by the New Jersey Air National Guard after the errant flight.

"If he went to the school and fired on it, obviously it would be of extreme concern," Wherley said.

The general said that without prejudging the investigation, he was "reasonably confident" the shooting was accidental.

Authorities have examined forensic evidence recovered from the school -- including eight rounds found in or on the one-story brick building and five in a parking lot. Based on that evidence, interviews and data logs generated by the aircraft and the air control center at Davis-Monthan Air Force Base in Tucson, the F-16 was flying at 7,000 feet, with the school miles out of effective range, when a quarter-second burst was discharged by the jet's 20mm cannon, Wherley said.

Four custodial workers were in the school at the time, including one who called police because she thought that people were running on the roof.

Wherley said the pilot was turning and possibly climbing over the Warren Grove bombing range, 41/2 miles from the school, preparing to make a strafing pass when the gun discharged.

Target runs typically begin at 3,000 feet altitude, and the weapon is considered accurate to about 6,000 feet, the general said.

The 20mm M61-A1 Vulcan six-barrel Gatling-type gun fires 6,000 rounds a minute. Investigators found 27 nonexplosive, hollow steel practice rounds -- each about seven inches long, four-fifths of an inch in diameter and weighing about a half-pound -- missing from the plane after the flight.

Wherley said the evidence indicates that the pilot did not "line up" to strafe the school. Because some rounds landed on the rooftop, instead of going into or through the building, Wherley said investigators believe they might have "rained" or arced down on the building from out of range.

New Jersey Air National Guard officials have said the pilot immediately told ground controllers that the gun had gone off.

"They are trying to determine whether it was a system failure or whether it was an actual pull of the trigger for another purpose," Wherley said. "The pilot is working with a lot of equipment up there, night vision, a laser targeting pod."

Officials have not named the pilot, a veteran in his thirties who has more than 1,000 flying hours in the F-16 and joined the Guard three to four years ago.

The 113th Fighter Wing has flown combat air patrol missions over the national capital area and other parts of the country since 2001. Two-thirds of the unit's members flew combat missions from western Iraq during the outbreak of fighting in 2003, Wherley said. The unit expects to resume flight training next week.

Residents and officials in Little Egg Harbor were briefed on the progress of the investigation last week. Lautenberg said constituent reaction has been mixed around the range, which has been the scene of an F-16 crash, accidental bombing and other problems in recent years.

"There will be no training at that facility," Lautenberg said, "unless we can guarantee that safety can be absolutely maintained."