At least 28 people were killed in a shoot-out between rival gangs in Mexico\'s Pacific coast state of Nayarit, the local prosecutor\'s office said in a statement. Security forces rushed to the scene of the battle at a highway intersection near the town of Ruiz, where \"they found 28 people dead, four others wounded and 10 abandoned vehicles.\" Local media quoted witnesses as saying the rival gangs had exchanged hails of gunfire and hurled grenades at each other for around an hour, as nearby shops closed up and terrified residents took cover inside. It was not immediately clear what sparked the shooting or whether the gunmen belonged to Mexico\'s powerful drug cartels, which often clash over lucrative smuggling routes leading from the coasts north to the United States. Mexico has seen an explosion in drug-related violence which has left some 37,000 dead, according to media reports, since the government launched a military crackdown on organized crime in 2006