Police had initially been investigating a reported kidnapping when they were alerted to the shooting nearby.
They found 28 men lying dead and four others wounded when they reached the scene littered with bullet shells.
Some 10 vehicles had been abandoned at the site.
More than 34,000 people have died in Mexico since President Felipe Calderon launched a crackdown on the country's drug cartels in December 2006.
Nayarit state has a strong presence of one of Mexico's most powerful drug gangs, the Sinaloa cartel, which is run by the country's most wanted man, Joaquin "Shorty" Guzman.
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