A letter was purportedly signed by the La Familia drug cartel announcing a one-month truce circulated Sunday in the western state of Michoacan, Mexico.

In the one-page message, distributed by e-mail and in some cities door by door, the gang claims it will halt all crime activity during January to demonstrate that the cartel "is not responsible for the criminal acts federal authorities are reporting to the media."

An AP report says that prosecutors have not verified the letter's authenticity.

The report says that La Familia has occasionally made public pronouncements seeking to convince the public that it is defending Michoacan against other drug gangs. Federal officials, however, say the cartel has terrorized the state with kidnappings, extortion, hundreds of murders, decapitations and drug trafficking, the report says.

More than 30,000 people have died in drug-related violence nationwide since President Felipe Calderon launched a crackdown on cartels after taking office in December 2006, first deploying hundreds of soldiers and federal police to his home state of Michoacan, says the report.

On Sunday, Calderon said in a New Year's broadcast that his administration will continue to fight organized crime, the report says. "We all know it is necessary to rid Mexico of crime, impunity and corruption, which had been rooted in our society and our institutions," he said. "I can assure you we are on the right path and we will defeat the criminals, to ultimately build a Mexico of peace."