BBC News, Mexico City
The entire police force in the Mexican city of Tijuana is to be investigated on suspicion of being involved in drug trafficking and organised crime.
Tijuana's mayor wants to clean up the city's police force
In an unprecedented move, the authorities say it is the only way to clean up the force.
Tijuana is on the American border and has been a major staging post for the supply of drugs to the United States.
Dozens of people have been killed so far this year in violent turf wars in the city.
In the words of Tijuana's mayor, Jorge Hank Rhon, everyone from the policeman on the street to the state superintendent will be the subject of this extraordinary investigation.
Mr Rhon says he believes that the majority of officers in his city are, in some way, involved in illegal drug trafficking or organised crime.
There are 2,300 police officers of one sort or another in Tijuana.
Mr Rhon had asked the federal authorities to intervene and now Mexico's ministry of public security has responded by setting up this wide-reaching inquiry.
A spokesman from the ministry said the details of what form the investigation would take would be released in the next two weeks.
The drastic move is believed to have been the result of pressure from businesses in Tijuana.
They set up an association to campaign against the influence of gangs in the city.
They threatened to move their companies elsewhere if nothing was done, a potentially devastating move in a city whose population is just over one million.
There have been efforts by the police to combat the influence of the drug gangs.
In August, the alleged head of the Tijuana drug cartel, Francisco Javier Arellano Felix, was arrested with the help of American authorities off the coast of California.
But the extreme violence has continued, prompting this unprecedented decision to root out corrupt officers who may be helping the cartels to supply drugs to the United States.