Sniffer dogs led authorities to the grisly discovery of three clandestine graves containing at least 33 bodies in a sugar cane field in Mexico's Pacific coast state of Nayarit, officials said Wednesday. Some of the bodies may have been hacked up before being tossed into the pits, and officials believe they were probably involved in the drug trade.

The discovery in the township of Xalisco comes amid a dispute between drug gangs in Nayarit following the March arrest of the former state attorney general, Edgar Veytia, on U.S. charges of drug smuggling.

Xalisco has long been the home base of a black-tar heroin trafficking ring that supplied the U.S. West Coast.

Current state Attorney General Petronilo Diaz said local gangs have been engaged in power struggles since Veytia's arrest. The victims found in the clandestine graves are believed to have somehow been involved in those disputes.

"The assumption is that these were people who were involved with one of the various criminal groups, but I can't say which one," Diaz said, adding that the burial pits "are the operational method of organized crime."

"This breakdown among the drug gangs we are seeing now in Nayarit comes as a result of the arrest ... of an official [Veytia] from the previous administration," Diaz said. "That is when these criminal groups start fighting, and that's when this mess we're seeing started."

Corrupt officials in Mexico have sometimes enforced a sort of rough peace by favoring one drug gang over the others or dividing territories.

The burial pits came to light when some families searching for missing loved ones found remains on Saturday after being tipped off by local residents. The first pit contained nine bodies and was located near a stream in a sugar cane field. Sniffer dogs then led searchers to two other pits nearby.

The bodies were so badly decomposed that neither their gender nor identity could be immediately established. The remains had been buried for about an average of six months, investigators believe.

They were pulled in pieces from the pits, and Diaz said some of them may have been hacked up before being buried.

"We are not ruling out the possibility that some of the bodies had already been dismembered," Diaz said.