Mexican police are today trying to establish whether two human heads recently found in a backpack match two headless corpses discovered yesterday.
The western state of Michoacan and Guerrero just to the south have been hit by a wave of beheadings and other gruesome murders this year as drug gangs fight for control of smuggling routes to the US and share of the local drug market.
The bodies were found in the trunk of a car in front of a grocery store in the state of Michoacan today.
The corpses carried no identification, and police contacted authorities in the state of Guerrero where two heads were found in a backpack yesterday to see if they match.
More than 2,000 people have died in two years in a war between the Gulf Cartel from northeastern Mexico and an alliance of traffickers from Sinaloa state. Other, smaller, drug gangs have also become involved in the feud.
Elsewhere, gunmen shot a man dead in the southern Mexican city of Oaxaca in the latest attack on protesters demanding the ouster of state governor Ulises Ruiz.
The man was reportedly hit by three bullets in a drive-by shooting as he left a meeting in the city, a popular tourist destination that has been paralysed by the protests.
Eight people have now been killed in the conflict that began almost five months ago when striking teachers and leftist activists occupied much of the colonial city, blocking hundreds of streets.
They say Mr Ruiz, from the Institutional Revolutionary Party, should step down for using heavy handed tactics to try to break a teachers' strike.
President Vicente Fox has vowed to end the conflict before he leaves office on December 1st.