Police in Mexico City say 12 people were trampled to death during a police raid in an overcrowded nightclub where high school students had gathered to celebrate the end of the school year.
Police chief Joel Ortega said nine young people and three police officers died. At least 20 people were injured.
Authorities said police went to the nightclub Friday to check reports that alcohol was being sold to minors.
Police said the club owner announced police had arrived, prompting students to stampede toward the emergency exit.
Ortega said many of the victims died of asphyxiation as they tried to flee through the emergency exit, which was blocked by cases of beer. The police chief said the club was packed well beyond capacity.
Police arrested 39 people, including the club's owner.
Some information for this report was provided by AFP, AP and Reuters.