Mexican police traditionally have had little or no training and are paid low salaries that make them vulnerable to corruption. Calderon launched his attack on organized crime in 2006 with the army because he said it was his most reliable force. Since then, he has expanded federal police from 6,000 to 35,000 with recruits who are fully vetted and better trained and paid. But even federal forces still have problems.
Ten federal police officers were arrested in the northern border city of Ciudad Juarez in September for running an extortion ring.
Mexico's army has taken over police operations elsewhere several times before, notably in Ciudad Juarez and the northern border state of Tamaulipas.
There was so little confidence in Ciudad Juarez police that two years ago, business groups there called for United Nations peacekeepers to quell the drug-related violence.
Tijuana, with what's known as one of Mexico's most corrupt police forces, has seen grandiose gestures aimed at restoring public confidence. In January 2007, federal authorities confiscated officers' firearms for ballistics tests to identify links to organized crime. Some officers carried slingshots in protest while waiting for their guns to be returned.
Starting in December 2007, 270 Tijuana officers on a force of about 2,500 were fired under suspicion of having links to organized crime, with 199 facing criminal proceedings. The effort was led by Julian Leyzaola, who was police director and later public safety chief from 2007 to 2010 and is now the top cop in Ciudad Juarez.
Since December 2010, 46 Tijuana officers have been fired for suspected criminal ties, officials say.
But Veracruz this week became the first Mexican state to completely disband a large police department and use marines as law enforcers. Even Calderon has conceded the Zetas have seized control of the state.
Duarte had already disbanded a police force in the state's capital of Xalapa, but in that case state agents immediately replaced city police.
Veracruz is a common route for drugs and migrants coming from the south on the way up to the United States. It was first dominated by the Gulf cartel, and then its former armed wing, the Zetas, took over after splitting from the cartel. The state saw a rise in crime this spring after a government offensive in neighboring Tamaulipas pushed drug criminals into Veracruz.
The port since has turned into a battleground between the Zetas and a gang aligned with the Sinaloa cartel, which is led by kingpin Joaquin "El Chapo" Guzman. The war in Veracruz reached a bloody peak in September when 35 bodies were dumped on a main highway in rush-hour traffic.
Less than a month later, authorities announced the firing of nearly 1,000 Veracruz state police officers for failing their tests.
Associated Press writers Katherine Corcoran in Mexico City; Porfirio Ibarra in Monterrey, Mexico, and Elliot Spagat in Tijuana, Mexico, contributed to this report.
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