At least 10 people were trampled to death Friday during a police raid on a packed nightclub in Mexico City, the capital’s police chief said.

Chief Joel Ortega said three police officers and seven youths, at least two of them minors, were killed. Several people were injured.

Police went to the News Divine club in northeastern Mexico City in the early evening to check reports of drugs and alcohol being sold to minors.

Ortega said about 1,000 young people were at the club celebrating the end of the school year and many more were waiting in line to get in. He said the crowd was bigger than the club’s capacity.

Ortega told the Televisa network the club’s owner announced to the crowd that police were there to arrest them, causing a stampede.

“A lot of the people concentrated at the club’s emergency exit, but it was to small” for them to get out, Ortega said.

Police detained 39 people including the club’s owner, he added.