Five bodies, including two headless corpses, were found Tuesday in the western Mexican state of Michoacan, officials said.
The bodies of three young men were found on a dirt road northwest of Morelia, the state capital, the Michoacan Attorney General's Office said.
The victims were all tortured and shot once in the head, the AG's office said.
The unidentified men were left lying face down in the dirt, prosecutors said.
The two headless bodies were found floating in the General Francisco J. Mugica Dam in Mugica, a city in the crime-ridden Tierra Caliente region, located about 250 kilometers (155 miles) from Morelia, the AG's office said.
The Tierra Caliente region, which takes its name from the high temperatures in the area, straddles Michoacan, Guerrero and Mexico states.
Investigators are trying to determine whether the headless bodies are those of brothers Apolinar and Jose Fernando Farfan Garcia.
The heads of the two men, who lived in the city of Gabriel Zamora, were found in Antunez, a town outside Mugica, last week.
Michoacan has been rocked by a wave of drug-related violence over the past few months.
Civilians began arming themselves last year to fight the Caballeros Templarios drug cartel, which operates across the state.
The Caballeros Templarios, a gang founded in December 2010 by former members of the Familia Michoacana cartel, deals in both synthetic and natural drugs.
The gang commits murders, stages kidnappings and runs extortion rackets that target business owners and transport companies.
The cartel uses Michoacan's 270 kilometers (168 miles) of coastline to smuggle chemical drug precursors for the production of synthetic drugs into Mexico.
The federal government deployed soldiers and police in Michoacan on Jan. 13 in an effort to end the wave of violence in the state.
Dionisio Loya Plancarte, one of the cartel's top leaders, was arrested by federal forces late last month. EFE