(CNN) -- A group of heavily armed men opened fire at a soccer match between two local teams in western Ciudad Juarez, Mexico, killing seven people and wounding two others, according to a municipal police spokesman.

The soccer field is at a community center opened four months ago as part of a program to decrease drug violence in a city that has been racked by violence and killings linked to drug cartels. Police said Monday they had not determined a motive for the shooting.

The dead from the shooting Sunday evening were males ranging in age from 19 to 26, police said. At least one was a soccer player -- an image from the scene showed the dead player face down on turf. Above him was a posted sign reading in Spanish, "Live Better" -- a slogan in Juarez's anti-violence campaign.

Three victims died at the scene, while four others died on the way to area hospitals.

The gunmen -- reportedly traveling in three vehicles -- sprayed the soccer field with about 180 rounds from assault rifles around 6 p.m., just before the game got started, police said.

Among the dead and wounded were several fans. Some of the victims were taken to hospitals by family members. One of the injured was a 12-year-old shot in the foot, the newspaper El Diario de Juarez said.

"We still do not have a motive why they opened fire," municipal police spokesman Adrian Sanchez told CNN in a phone interview from the scene. "They fired 180 rounds in three or four seconds. It happened fast," Sanchez added. "People here are still confused about what happened."

Journalist Arturo Chacon contributed to this report.