One teenager was killed and 10 other people were injured yesterday at St. Albans School in Northwest Washington when lightning from a powerful afternoon thunderstorm struck a group of spectators standing beneath a tree as they waited for a lacrosse game to resume.

Witnesses said one bolt of lightning hit the group about 5 p.m., shortly after a championship match between St. Albans and Landon School of Bethesda, two of the Washington area's most prestigious private schools, was abruptly halted amid pouring rain. Hundreds of people had raced for cover, witnesses said, and some had stopped under the large trees that line the St. Albans grounds, near the tennis courts at 35th and Garfield Streets NW.

"There was a loud noise, and the kids standing next to me just fell like cards," said Carol Lubetzky, who was beneath the tree that was struck. "My ears were ringing . . . . One guy turned blue, then white."

The dead youth was identified by D.C. police as Noah Eig, 15, of the 3700 block of Thornapple Street in Chevy Chase. Eig, a freshman at Landon, was the son of Michael J. and Emily Eig, a Landon spokesman said.

The others injured by the lightning were six youths and four adults. Some victims were burned, and at least two of them lapsed into cardiac arrest at the scene, officials said.

Jessica Barton, 17, who was treated at Suburban Hospital in Bethesda last night and released, said she was trying to find a ride when the lightning struck.

"There was a huge boom, and a bright orange light," said Barton, who is a student at Holton-Arms School in Bethesda. "I felt a burn on my forehead. It was very hot."

Others injured were identified as: Tal Alter, 15, in stable condition at Georgetown University Hospital; Melissa Burton, 17, taken to Suburban; Jeffrey Cohen, 15, in stable condition at Georgetown University Hospital; Josh Guttman, 16, in stable condition at Georgetown; Fred Laughlin, 44, in critical condition at Georgetown; Tom Malatesta, 48, in stable condition at Georgetown; Jay Parker, 11, in fair condition at Georgetown; Claudia Parker, 42, taken to Suburban; and Ginger Snider, 45, in critical condition at Georgetown.

The thunderstorm swept swiftly across the Washingon area yesterday evening, snapping tree limbs, causing minor flooding and traffic jams and leaving several thousand residents without electrical power.

Weather officials said the storm, which at times packed 40-mile-per-hour winds, brought frequent lightning because of the heat and humidity of the day. But because its winds were sporadic and there was little hail, officials said the storm was not extraordinary.

"This was just a typical summer storm," said Patrick Moore, of the National Weather Service. "One lightning bolt can do a lot of damage."

A crowd of family and friends of the victims gathered at Georgetown University Hospital last night. Those who witnessed the strike said that some of the victims were leaning against the tree waiting for parents when the lightning struck.

Witnesses described a sudden flash that seemed to strike the middle of the tree, which was about five stories tall, and said most of those injured appeared to be burned, not hit by falling limbs.

Witesses said dozens of people fell to the ground or ran when the lightning struck. Some people shouted for medics. A few doctors among the crowd, which numbered about 1,000, rushed to give two of the victims cardiopulmonary resuscitation. For an hour afterward, frantic parents arrived at the school, some leaving their cars in the street, and yelling for their children.

Shortly after the incident, an ambulance collided with a car a few blocks from the scene. Two people in the ambulance were slightly injured, and the driver of the car, who has not been identified, was taken to Georgetown University Hospital and listed in critical condition. It was not clear last night if the ambulance had been on its way to help the victims.

Some spectators at the game said that in their hasty retreat from the lacrosse playing field, several people did not stop to consider the danger of standing beneath a tree in a storm. Others said that some stood near the trees because a small shelter near the field and the school's tennis courts was filled with people.

"You would think none of us had a brain in our head," said Lubetzky, the teacher who was standing next to the tree. "We all know not to go under a tree, but so many of us did it. It was all such a shock, such a horrible thing."

Dick Allanson, the assistant athletic director at St. Albans, said officials supervising the lacrosse game stopped play when lightning was first spotted in the dark sky. Allanson said the game had been halted for about 10 minutes when the lightning hit the tree, and that St. Albans team members had returned to their locker room. Witnesses said the Landon team went to its bus. St. Albans was leading 2-1.

Medical officials said last night that victims of lightning who survive usually recover most of their faculties, though it may take some who have suffered damage to their brains months or longer to recover fully.

"Lightning carries a million volts of electricity," said Andrew Munster, director of the Baltimore Regional Burn Center. "Anybody who sustains a direct hit will likely die on the spot."

Irregular heartbeats, brain swelling and deep tissue burns are the most common and serious injuries that lightning victims suffer.

Because most people are standing when struck, the skull and the brain often receive the most electricity, Munster said. The injured brain often swells and presses against the skull, which can be life-threatening. Lightning also may cause burns. Beneath the skin there can be fourth-degree burns that singe bones. Some cases require surgery and amputation.

Aside from the incident at St. Albans and the nearby crash, there were no other serious injuries reported from yesterday's thunderstorm, which for all of its havoc did not leave more than an inch of rain. Weather officials said the storm quickly cleared the area after striking right near rush hour.

Fire officials in Prince George's County said the storm caused minor accidents and scores of downed power lines. Several instances of flooding were reported near the Capital Beltway.

In Fairfax and Prince William counties, power outages left traffic lights dead at many intersections and cause heavy traffic problems. Prince William officials reported two dozen minor traffic accidents.

Nearly 6,000 homes were without electric power in the Northern Virginia area for several hours last night.

Staff writers Patrice Gaines-Carter, Mary Lou Foy, Joel Garreau, Veronica T. Jennings, Carlos Sanchez, Sally Squires, Gene Wang and Debbie Wilgoren contributed to this report.