Prisoners Escape in Mexico Left Dead Rivals

[From article]
"four top prison officials had been fired from their jobs, as had 18 guards on duty at the time of the incident. All were being investigated for complicity,
[. . .]
Two years ago, the government arrested the prison director and guards at one facility in the state of Durango, where officials provided arms and transport for Sinaloa gang members who were allowed out every night to kill their Zeta rivals. The inmates, who were involved in a number of drug-related killings, including the massacre of 17 people at a restaurant, would then return to sleep at the prison."

http://online.wsj.com/article/SB10001424052970203358704577235411760082478.html?mod=googlenews_wsj

Jail Riot in Mexico Was Diversion for Escape
By JOSE DE CORDOBA
February 21, 2012
Wall Street Journal