The Mexican government announced Monday it has replaced the federal police chiefs in all 31 states and the Federal District to determine whether they are fighting drug trafficking or abetting it. The move comes as President Felipe Calderón is now six-months into an offensive against the powerful and violent so-called cartels that has seen more than 20,000 soldiers and police swarm into cities and states considered hotbeds of the drug trade.

The 32 purged chiefs must submit to and pass polygraph and drug tests before being reconsidered for their positions. Their financial status will also be scrutinized. If they pass muster, they must be retrained before being reassigned.

Drug prohibition-related corruption has been the bane of Mexican law enforcement for decades. Now, once again, a purge of police is viewed as necessary by high officials. Just last month, six federal police officers were arrested for protecting cocaine shipments at the Mexicali airport.

"Every federal cop is obliged to carry out his post with legality, honesty and efficiency," Public Safety Secretary Genaro García Luna said at a news conference Monday announcing the housecleaning. "In the fight against crime, we have strategies. One axis of our strategy is to professionalize and purge our police corps."

Nearly 7,000 of Mexico's 20,000 federal police, who investigate drug crimes and homicides, have been assigned to work alongside the more than 12,000 soldiers deployed in Calderón's war on drugs. That police are working side by side with soldiers has raised concerns that they could be undercutting Calderón's campaign by passing information on to the drug traffickers.