Two 15-year-old Temple Hills youths have pleaded guilty in Prince George's County Juvenile Court to charges stemming from six rock-throwing incidents on the Capital Beltway last summer, Maryland State Police said yesterday.

The youths, who are not suspects in Sunday's Beltway rock-throwing, were given probation and ordered to pay restitution after they pleaded guilty Wednesday to misdemeanor charges of reckless endangerment and malicious destruction of property, State Police Detective Michael White said.

"These kids started getting very serious in their actions," White said. "Normally, kids throw one rock and run and that is the last we see of them."

The youths who pleaded guilty are students at Crossland High School and Walker Mill Middle School.

They threw rocks, bottles, bricks and pieces of wood from the Auth Road overpass and the nearby shoulder of the Beltway in southern Prince George's County on six occasions during June, July and September, White said.

Twenty-one vehicles were damaged and several people incurred minor cuts in the incidents, most of which took place in the late afternoon and early evening hours, White said.

One youth told investigators that throwing rocks was "just something to do," White said.

In Sunday's rock-throwing, seven people were injured and 25 vehicles were damaged on the Beltway near Livingston Road.

The most seriously injured, Destiny Morris, 15, remained in critical condition yesterday in intensive care at Southern Maryland Hospital Center.

She was struck in the head by a rock that crashed through the window of the pickup truck in which she was riding, police said.

State Police said yesterday that they are continuing their search for three youths, between the ages of 14 and 18, who had been seen standing in the traffic lanes of the Beltway.

The teenagers who pleaded guilty Wednesday were arrested in February after acquaintances told officers that they had been asked to join in throwing rocks, White said.

"After a lot of searching, we found some kids who had witnessed these kids in the area just prior to one of the occasions," White said.

"The kids that we found mentioned that they were going to go throw rocks and said where and asked if these other kids wanted to come along."

Diane Merchant, a Prince George's County resident whose station wagon windows were shattered in one of the incidents, attended the court proceeding Wednesday, prepared to testify.

"The whole back window just collapsed inward. And it is really fortunate that no one was sitting in the back," said Merchant, who added that her three children, aged 10, 5, and 4, received scratches.

Merchant said that several other victims were waiting in the hallway for a trial to begin when the youths changed their pleas to guilty.