WEST HARTFORD — - Secondary school administrators sent letters to parents Friday after cellphone video footage was discovered of Conard High School students playing a potentially deadly game in which a person intentionally passes out to achieve a high.

Conard Assistant Principal Roszena Haskins said the video showed one male student depriving himself of oxygen as three other male students watched. Another student who later saw the video was disturbed enough to notify an adult after-school on Thursday.

School officials then identified all of the students seen in the video and met with them and their parents on Friday morning, Haskins said. She said the first priority was to check on the welfare of the student who was shown actively taking part in the "Passing Out Game," also known as the "Choking Game."

He was not injured, Haskins said, and in the video appeared to walk away. It was unclear to school officials where the video was taken.

The letter warns against playing the game and lists warning signs that someone may be playing.

"We're really focused on education and helping students understand the implication of this kind of game and what it means in terms of their health," Superintendent of Schools Dr. Karen L. List said.

Haskins did not say whether the students would face discipline. "The school has taken appropriate action to collaborate with parents and just increase the knowledge and dangers of this, so I think it's been addressed," she said.

According to the Center for Disease Control, older children or adolescents play the game to achieve a brief high by depriving the brain of oxygen. They either choke each other or themselves.

The game is played nationwide, is known by a variety of names and can lead to serious injury or death. In 2006, a 12-year-old Evan O'Connor of Stamford accidentally choked himself. Similar incidents have occurred across the country.

The CDC says there have been 82 probable choking-game deaths among youths aged 6-19 years from 1995 through 2007.

"Unfortunately many students seem to be unaware of the extreme dangers associated with this behavior and the potential for death," Thomas Moore, Conard High School principal, said in the letter to parents.

Some warning signs that someone is playing the game include bloodshot eyes, discussions of the game, marks on the neck, severe headaches, wearing high-necked shirts, irritability or hostility, or ropes, scarves and belts tired to bedroom furniture or doorknobs.

For more information visit: www.cdc.gov/features/chokinggame/