HOHHOT - Seven teenagers have drowned in a reservoir in a county in North China's Inner Mongolia autonomous region, local authorities said Monday morning.

The tragedy happened when the seven, all high school students, went for a swim along with friends in Budong River Reservoir in Shangdu county Sunday afternoon, a spokesman of Shangdu county government said.

Staff from the reservoir said they heard the students crying for help at around 4:46 pm Saturday and immediately called for rescuers.

The seven students, all boys, were pulled out of water after more than 140 armed police and fire fighters searched for two hours. They were rushed to the hospital, but died after emergency medical treatment failed.