Mexico City's mayor expressed outrage Saturday that youths as young as 13 were among the dozen people killed in a nightclub stampede and said the officials involved in the police raid that sparked the crush had been suspended.

Police went to check reports of underage drinking and drugs in the News Divine club in a working-class Mexico City neighborhood Friday evening, causing hundreds of customers to try to flee the club.

About 500 young people — more than the club's capacity — had packed the bar to celebrate the end of the school year, according to police. Witnesses and police said the only emergency exit was blocked, and desperate customers tried to break out windows to escape the crush.

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"The city is indignant," Mayor Marcelo Ebrard told a news conference. "What we saw yesterday was ethically unacceptable."

City prosecutors said three young teens — ages 13, 14 and 16 — were among the nine students and employees who died. Three police officers also died at the club in Mexico City's Nueva Atzacoalco district. A dozen people were injured in the stampede, three seriously, said city prosecutor Rodolfo Felix Cardenas.

City officials said all the public servants directly involved in the raid have been suspended, including the police director who led the action.

Julieta Coronel Mejia, whose two nieces were injured, said police entered the club and began pushing people, possibly helping spark the stampede.

Ebrard acknowledged that there were "serious errors" in the raid and apparent irregularities in the operation of the bar. "This place should not have been operating," he said.

Juan Carlos Maya, a club employee and the brother of owner Alfredo Maya, acknowledged that alcohol was being served but said patrons were asked for identification at the bar. The legal drinking age in Mexico City is 18. The club was holding one of the afternoon "tardeada" parties that are popular among clubbers as young as 16, though only patrons 18 and older are allowed to drink alcohol.

Maya said he could not explain why the 13- and 14-year-olds were inside. His brother and three others, all apparently club employees, were being held as suspects in the case. Maya acknowledged the club had been closed for violations in the past.

But he showed the club's liquor license and an inspection certificate from 2007 and said police blocked the emergency exit, apparently to prevent suspects from escaping.

Police Chief Joel Ortega said the exit was obstructed by cases of beer. Ortega denied reports that officers threw tear gas inside the club.

Television images Friday night showed glittery high-heel shoes and T-shirts strewn over the dance floor. Bodies covered with white sheets lay by the club's entrance.

Dozens of riot police were sent to control a crowd of sobbing relatives and friends that gathered at the scene.

The tragedy revived memories of a 2000 fire at a glitzy Mexico City nightclub that killed 21 people. The emergency exit at the Lobohombo nightclub was locked with a chain. Few people were ever brought to justice for the deaths.