Two teenage siblings and a Fairfax County man were killed yesterday when the young driver of the station wagon they were riding in drove into the path of a dump truck in St. Mary's County, Maryland State Police said.

David C. McGinnis, 14, and his sister Nicole A. McGinnis, 16, both of whom were in the back seat of the car, were pronounced dead at the scene of the accident at Route 235 and Route 6, not far from their home in the small St. Mary's community of Mechanicsville. A front-seat passenger, John A. Baker, 33, died at Prince George's Hospital Center, authorities said. It was not immediately clear what his relationship was to the other passengers, police said.

The 16-year-old driver of the car, whom police did not identify, and her 14-year-old sister, who was sitting in a rear cargo area of the station wagon, were treated at Washington Hospital Center for what authorities described as non-life-threatening injuries. All the teenagers were on break from Chopticon High School in St. Mary's, where classes were not in session because of teacher training, authorities said.

In a state where traffic accidents are the leading cause of death among residents ages 15 to 20, yesterday's crash was another in a string of highway tragedies involving young people in Southern Maryland. From summer 2001 to summer 2002, several automobile accidents in the area killed at least nine teenagers, including a 16-year-old Chopticon student.

"I've been at [Chopticon] for 14 years, and I can't think of a year in which we didn't lose at least one student," Tony Lisanti, basketball coach for the girls team at the school, said yesterday. "If the kids don't worship the automobile, they're definitely auto-centered. There's no real town here. You have to drive to everything."

The driver of the 1989 Chevrolet Celebrity wagon in yesterday's crash had only recently obtained her license, authorities said. She was heading west on Route 6 and was trying to cross Route 235 about 12:30 p.m., said Lt. Brian Cedar of the state police.

He said the driver stopped briefly at a yield sign in the median between the northbound and southbound lanes of Route 235 and then drove forward into the path of the dump truck, being driven by William T. Brown, 50, of Charles County.

"She apparently thought she had time to get across," Cedar said.

The crash was still under investigation last night.

Lisa Bugelisi, a clerk at Korner Karryout gas station near the accident, had finished mopping the floor when she saw the vehicles collide. "I thought the dump truck was just going to clip the front of the car," Bugelisi said. "He hit them full on and pushed them."

She called 911 after two men at the scene told her to stay away because there are "five people inside and only one is moving," she said.

Cedar said the father of the siblings who were killed arrived at the crash site shortly after the accident and had to be restrained by police from attacking Brown. "I had to tackle him," Cedar said.

The dump truck left a skid mark 260 feet long as it pushed the car down the side of the road, Cedar said. Glass and twisted metal were strewed along the southbound side of the highway, which was closed for four hours. Brown, an employee of J and T Trucking in Calvert County, was not injured.

On July 26, 2001, a Chopticon student and an 18-year-old recent graduate of the school were killed in a car wreck. Six months later, two siblings, both students at Lackey High School in Indian Head, died in an automobile wreck, with a third teenager.

Another Lackey student and a former student died March 11, 2002, in an accident. Three months later, in Charles County, two high school students died in a crash.