A race of 52 hot-air balloons to benefit a children's charity turned into disaster early yesterday near Gaithersburg when a propane-laden balloon hit a high-voltage power line, caught fire and exploded, killing a 16-year-old girl and seriously burning her father, who was piloting.

The 75-foot multicolored balloon, piloted by Robert Van Newkirk, 39, of Pittsburgh, struck a 69,000-volt Pepco transmission wire as he and his daughter, Kristine Lynn, attempted to land in a clearing off Goshen Road about 7:20 a.m., after a three-mile race, authorities said.

"Suddenly, you could hear the explosion and there was this huge fireball . . . . I saw this ball of fire as this thing exploded, and we heard the young girl scream," said Donald Brown, 59, a Chesapeake & Potomac Telephone Co. engineer who saw the explosion from his home on Goshen Road.

The balloon and gondola plummeted, Brown said, and "I saw this man lying on the ground, rolling on the ground to put the fire out, because he was on fire."

"The man was on the ground, still alive, and he was saying 'My girl . . . somebody take care of my little girl,' " said James Fisher, who rushed to the scene from his home on nearby Sandpiper Lane in a community of town houses. " . . . It was awful."

The flotilla of colored balloons, which were launched about an hour earlier from the grounds of Comsat Laboratories in Clarksburg in upper Montgomery County, had attracted a small group of upcounty residents who left their homes, some with cameras, to witness the event.

But onlookers quickly were turned into rescuers.

Wallace Henderson, a Vienna balloonist for 11 years, landed in the clearing just before Van Newkirk. "I had deflated my balloon . . . and saw {Van Newkirk} coming very low over the trees. I saw it hit the power lines, and arc, and the propane flare."

Henderson said he then saw the gondola separate from the balloon.

"There was another explosion, and the basket came loose {from the wires}, dumping the pilot out.

"The basket came down and hit. It was on fire, and the propane tank blew up," he said.

"My son Phil and two others pulled {the pilot} out of the fire area around the basket . . . . The girl was in the middle of the fire. They didn't know she was there until the pilot asked about his daughter. Things happened very rapidly."

Kristine Lynn, described by family members as a bright high school sophomore and an adventuresome companion to her father on weekend balloon outings, was pronounced dead at the scene. Van Newkirk, a sixth-grade teacher in North Hills, Pa., was flown to Washington Hospital's MedStar Unit, where he was in serious condition with second-degree burns on his chest, arms and back, a broken pelvis bone, a broken rib and cracked vertebrae, family members said.

The Federal Aviation Administration, along with Montgomery County police and fire officials, were at the scene of the crash in the 18400 block of Goshen Road, and the National Transportation Safety Board also was expected to investigate.

The balloon -- carrying propane tanks as fuel for its hot-air heater -- hit the high-tension wire alongside a stand of tall, bushy evergreen trees as it was approaching a clearing near town houses off Quail Valley Boulevard. Several other balloonists had already landed there, and were awaiting radio-dispatched "chase cars" to help disassemble and transport their rigs.

Van Newkirk's wife Maryann and younger daughter Laurie were in his chase car, heading for the landing site, when the explosion occurred.

Authorities and family members speculated that the tall trees might have obscured Van Newkirk's view of the power line. Balloonists frequently allow trees to brush the bottom of their gondola to slow the lateral speed during landings.

Richard Drews, a 43-year-old sales manager, said the second explosion "sent up a fireball" and set pine trees on fire.

"I could feel the heat," said Drews, who ran to the scene from his house about 300 yards away.

The striped balloon separated and flew off after the gondola fell about 30 feet, scorching several trees as it dropped, authorities said.

The "hare-and-hound" balloon race had started at the sprawling Comsat property off I-270 as part of a two-day fund-raising event for Kids Inc., a local organization that raises money to grant wishes to terminally ill children.

The third annual Kids Hot Air Balloon Rally was to raise up to $15,000 for the children through various concessions, according to John Campbell, the group's executive director.

The first balloon, the hare, flew about three miles southeast from Comsat and landed near Rtes. 355 and 27, north of Gaithersburg. The crew left a large X there to mark the spot where the race ended.

The "hounds" competed by trying to chase the hare and drop a marker as close as possible to the X, with the nearest marker winning.

Then, each pilot was to drift further, finding a landing spot and using a two-way radio to summon the chase cars.

Brown, the phone company engineer, was a witness to the explosion, which happened while he was cleaning the swimming pool in the yard of his house in the Sharon Woods subdivision.

Multicolored balloons were flying overhead, but two large balloons had landed in the nearby field.

"When the second balloon landed, I thought this was their flight plan," he said.

Brown said he ran inside his home to tell his 22-year-old daughter Amy about the balloons, "and we were looking out our window when the third balloon apparently hit the power line."

"This is not anything you ever forget," Brown said.

Van Newkirk's brother Gary, reached in Pittsburgh, said his brother was an experienced balloonist who took up the sport three or four years ago and bought a used balloon.

"Kristy always went up with her dad" and was very close to him, he said.

Maryann Van Newkirk, who had been carrying a walkie-talkie, told her brother-in-law in a phone call that she believed the power lines may have been hidden by the trees. The crash "was out of her view," Van Newkirk said.

Gary Van Newkirk said his brother, who teaches at Seville Elementary School, is "a real easy, outgoing guy, constantly active," who imparted his sense of adventure to his oldest daughter.

He described Kristy as full of life. "When she walked into a room," he said, "it just came alive." She was "a real good student" and a flutist in the school band.

Ballooning enthralled "the whole family," he said. They liked the excitement and the feeling of free flight. They tried to do it "every chance they could get, at least one or twice a week. Just about every weekend, they were going up somewhere," he said.

Just last week, he said, his brother tied up his balloon in a school yard and took children about 100 feet up for a brief ride.

"Everything was going great for them," he said.

National Transportation Safety Board statistics show deaths in balloon accidents are relatively rare. No one died in 1984, when 34 accidents occurred. Three persons were killed in 1983, when 29 accidents were reported. Seven people died in 1982.

But yesterday brought two deaths on the same day. A 26-year-old Charlotte, N.C., man who received a balloon ride as a wedding gift was killed when the balloon became tangled in power lines near Charlotte. His wife was not injured.

The pilot told authorities that the sun blinded him and he could not see the power lines.Staff writer Joseph E. Bouchard contributed to this report.