YOSEMITE NATIONAL PARK, Calif. (AP) _ Five hikers who were struck by lightning atop the park's Half Dome attraction ignored warnings against climbing to the peak of the granite monolith, rangers said.

Three of the hikers were injured and two killed during the electrical storm, including one man who was struck in the forehead, slipped from his companion's arms and died after falling 1,800 feet, rescuers said.

The group was struck twice by lightning after climbing to the peak of the 8,842-foot monolith, one of the park's most popular tourist sites. Signs along Half Dome trail warn hikers against climbing to the top because of electrical storms, rangers said.

One of the dead was identified Sunday as Brian Jordon, 16, of Hayward. The name of the other fatally injured hiker was withheld pending notification of relatives, according to a park statement.

Tom Rice, 28, of Los Gatos and Bruce Weiner, 24, of Mountain View, were listed in critical condition at University of California-Davis Medical Center.

Adrian J. Esteban, 24, of San Jose, was treated at the park medical clinic for minor injuries and released.

The lightning struck about 6:30 p.m. Saturday as the group of five huddled in a cavern for protection against a sudden storm, according to paramedic Bill Bryant.

The unidentified man was struck by a bolt and went into convulsions, jerking toward a ledge as one companion tried to hold him. The victim ''was shaking so hard that his friend finally had to let him go for fear of his own safety,'' Bryant said. The man rolled off the edge and his body was recovered Sunday.

Another bolt struck 15 minutes later, and when the storm abated, Esteban struggled to summon help from another group of campers, Bryant said.

One of the campers hiked 81/2 miles to the valley floor and reached rangers at about 9 p.m. A helicopter evacuated the victims around midnight, accoding to park spokeswoman Lisa Dapprich.

''We only had about two hours of moonlight to work with and were barely able to get them out of there,'' Bryant said. ''It was a real close race with time.''

Electrical storms occur frequently in the Sierras during summer, Dapprich said, and signs are posted urge hikers to stay away from mountain peaks.

''All the way up and down the Half Dome trail there are signs warning about lightning and telling people not to go to the top because of the danger,'' she said.