An 18-year-old Reston youth was severely burned Tuesday afternoon when he touched a 19,900-volt electriton, Fairfax County police reported.

Police also said a half pound of marijuana and a marijuana smoking device were found inside the vault but added they knew of no connection between the youth and the marijuana. Police said an investigation is continuing.

The youth, Christopher Cherry of 1542 Goldenrain Ct., was listed in serious condition yesterday in the burn unit at the Washington Hospital Center. A hospital spokesman said Cherry suffered second and third-degree burns over 14 percent of his body.

Cherry is a college freshman home on spring vacation from Virginia Commonwealth University in Richmond, according to police.

Police said Cherry apparently was reaching into the Virginia Electric and Power Co. electrical vault, a metal room about 10 feet square containing electrical switching devices, when he touched the high voltage wire. The youth's feet, police said, apparently were outside the vault on wet grass.

The marijuana and the smoking device, police said, were found inside a cigar box stuffed into a crevice in the electrical equipment.

Jack Hornsby, district manager for Vepco in the Reston area, said the vault appeared to have been broken into. "You really have to make one heck of an effort to break into one of those things (vaults)," Hornsby said.

The vaults have signs that warn of high voltage.

About 3 p.m. Tuesday, police said, a passerby heard screams and found the injured youth. An ambulance took Cherry to Reston Access Hospital whence he was flown by helicopter to the Hospital Center.

Richard Leper, an administrator with the shock trauma unit at the Hospital Center, said that 19,900 volts is "definitely with the lethal range."