About 5,000 people are said to have died in drug violence this year
The bodies of 13 people have been found on a dirt road in Mexico's Sinaloa state, home to one of the country's most violent drug cartels.
The victims' hands were bound and all had been shot. Most were teenagers.
Passersby found the bodies near a stolen truck in the northwest of the state on Thursday.
It comes a day after a leading newspaper, El Universal, said that at least 5,000 people had been killed in drug-related violence this year.
A local prosecutor, Juan de Dios Beltran, said the police were still trying to identify the victims.
President Felipe Calderon has deployed more than 40,000 troops to combat drug traffickers.
However, drug violence in Mexico is rising as gangs fight each other and the security forces.
In October, drug traffickers killed 11 people in a bar in Ciudad Juarez.
In August, 11 beheaded bodies were dumped in the country's south. In the same month, 13 people, including a baby, were killed in a tourist town in the north.
The government is also struggling to clean up its security forces.
Last month, Noe Ramirez Mandujano, the ex-head of the anti-organised crime agency, was arrested as part of an investigation into links to drug cartels.
The attorney general said Mr Ramirez accepted $450,000 (£305,897) from cartels and was offered a monthly fee for information.
Other senior officials have been detained as part of an operation to crack down on corruption.