Ciudad Juarez, Mexico - Gunmen killed six young men at a family party in the gang-plagued Mexican border city of Ciudad Juarez, prosecutors said Sunday.

The men, ages 20 to 25, were killed during a party in a house, said Alejandro Pariente, a spokesman for the regional attorney general's office. The motive for the attack was unknown.

At least 1,000 people have been killed this year in Ciudad Juarez, a city across from El Paso, Texas. Many of the deaths were attributed to warring drug gangs.

In the border city of Tijuana, across the border from San Diego, federal police announced the arrest of seven reputed members of a cell of the Arellano Felix drug cartel, including a city police officer.

The suspects holed up in a Tijuana house Saturday and opened fire on police, the Public Safety Department said in a news release. Local news media reported that neighboring homes were evacuated and police apparently used tear gas to flush out the gunmen.

The officers seized 21 assault rifles, 4,000 rounds of ammunition and body armor in the raid.

Authorities reported on Friday that 91 people have been killed throughout Tijuana in a wave of gangland homicides since Sept. 26.