Twenty-two people were found shot dead in northern Mexico, including four found on property belonging to the state-run oil giant Pemex, police said.
The killings late on Monday and Tuesday are likely the result of the ongoing war between powerful drug cartels for control of lucrative access corridors to the United States, officials said.
Petroleos de Mexico workers found the bodies of the four men, some half-dressed and with tape over their eyes, piled up in a well on company property some 150 kilometers northeast of Monterrey, on the US-Mexican border.
The men had all been shot in the head, police in this prosperous and heavily industrialised city told AFP, speaking on condition of anonymity.
Meanwhile to the west in the state of Chihuahua, a state also bordering the United States, police found 18 bodies.
Among the dead were three men were found Tuesday afternoon in the state capital Chihuahua with their hands and feet tied. Police said that witnesses saw how the victims were forced out of a vehicle and riddled with bullets on the spot.
Other bodies were found in different state cities, including five in Ciudad Juarez, the epicenter of a war between the Juarez and Sinaloa drug cartels. Already 116 people have been killed in drug violence in Juarez in 2009.
In 2008 some 2,400 people were murdered in Chihuahua state, 1,600 of them in Ciudad Juarez, according to government figures.
The Mexican government has deployed some 36,000 soldiers across the country to battle organised crime.