The bodies of 17 men, most of them tied up in chains and shot dead, were found dumped along a highway Sunday in a western Mexican state known as a violent battleground for rival drug cartels.
Police found the bodies amid an upsurge in drug gang violence following the arrest of two major drug lords in recent weeks.
"Witnesses said that some people arrived in vans, threw out the bodies and left," said Jalisco state prosecutor Tomas Coronado. "They were practically all tied up with chains."
Coronado said the men may have been killed elsewhere and left in his state, since Jalisco borders on Michoacan, and both are among the states most ravaged by the country's drug violence.
The bodies were found near the farm town of Tizapan, close to the state border with Michoacan, officials said.
There have been no arrests, and no group has claimed responsibility for the crime.
Some 60,000 people have died in drug-related violence in Mexico since President Felipe Calderon ordered federal troops to take on the cartels in late 2006.
The war between cartels is mainly over lucrative drug smuggling routes to the United States, but also over control of local crime rackets.
The violence seems relentless. On Friday alone, 16 dead bodies were found in northern Mexico.
Nine of those dead were found hanging from a bridge in the northern border city of Nuevo Laredo, a killing spree authorities blamed on drug gang violence.
Some 40 percent of Mexican exports sent by land to the United States cross through Nuevo Laredo, making the town a choice site for drug smugglers.
Authorities have warned of an increase in gang violence following Wednesday's arrest of Jorge Eduardo "El Coss" Costilla, the top boss at the Gulf drug cartel, one of the country's seven powerful crime syndicates.
Costilla's arrest came one week after authorities detained Mario Cardenas, another top Gulf Cartel leader.
The country's two main drug gangs -- the western Sinaloa Syndicate of Joaquin "El Chapo" (Shorty) Guzman and the paramilitary Zetas gang -- will likely make a move for the Gulf cartel's crime networks, analysts said.