Two Montgomery County teen-agers were killed early yesterday when a fire engulfed their parked car, county police reported.

Police identified the victims as Louis Douglas Hannaway, 17, of 10609 Gainsborough Rd., and Mary Carter Barrow, 16, of 8107 Postoak Dr., both in Potomac.

Officials said they have not determined the cause of the fire or why the victims, both students at Winston Churchill High School, failed to get out of the car.

Police spokesman Philip Caswell said yesterday police were speculating that the teen-agers may have fallen asleep or passed out from carbon monoxide poisoning before the car, which was parked in front of a house at 12025 Smoke Tree Rd., Potomac, caught fire.

"It would appear that the fire didn't start in the interior of the car," Caswell said. "It may have started under the hood."

According to Caswell, the two teen-agers and another girl, who he declined to identify, had attended a party earlier in the evening.

The teen-agers dropped the girl off at her home around 1 a.m., he said. Sometime after 2 a.m., Hannaway apparently parked the car in front of the Smoke Tree Road address, Caswell said. Neither of the teen-agers knew the occupants of the Smoke Tree Road home, he said.

Two persons driving home spotted the car, by then already in flames, shortly after 3 a.m. Caswell said. They alerted a neighbour, who called the fire department.

Once firemen extingusihed the fire, the two bodies were discovered inside, he said. Hannaway, who was a football player, was found in the front seat and Barrow's body was in the back seat, Caswell said.

Most of the front of the car was burned, which led some officials to theorize that the two may have succumbed to carbon monoxide poisoning. He said firemen were able to put out the fire before it reached the gas tank in the rear of the car.

Caswell said Hannaway and Barrow were simply friends. Neighbors described the two teenagers as good students.