15 students in Mexico treated after taking part in internet tranquilizer "challenge" to see who can stay awake the longest

Fifteen grade school students in Mexico have been treated after apparently taking part in an internet "challenge" in which groups of students take tranquilizers to see who can stay awake the longest.

The incident occurred Monday in the north-central city of Guanajuato. It came just days after health authorities issued a national alert about the craze. It was the fourth school in Mexico to suffer such incidents in the last year.

Guanajuato Mayor Alejandro Navarro said the students were treated at the school, and urged parents to supervise their kids' use of social media.