22 February 2012 Last updated at 01:33 GMT Mexico violence: taxi drivers gunned down in Monterrey Five taxi-drivers have been shot dead in the city of Monterrey in northern Mexico, the authorities say. Gunmen with assault rifles fired on the drivers as they waited for passengers at a taxi-rank in the mid-morning. The motive for the attack is not known, but it is thought nike nfl jerseys they may have been targeted by criminal gangs who extort money from local businesses. Monterrey is a prosperous industrial city, but in recent years it has become cheap nfl jerseys a focus of drug-related violence. The city has become a battleground for the rival Zetas and Gulf drugs cartels, who are fighting for control of smuggling routes into the US. On Sunday 44 prisoners were killed during a riot at a jail outside the city, and 30 other inmates escaped. The prison director and guards have been accused of colluding in the break-out by prisoners linked to the Zetas. Last year Monterrey was the scene of the one of the deadliest incidents Mexico has seen in recent years wholesale nba jerseys - an arson attack on a casino which killed 52 people. It was also blamed on extortionists.