(CNN) -- The 49 decapitated bodies authorities found on a roadside in northern Mexico over the weekend were likely the result of a fierce feud between rival drug cartels, a top Mexican official said Monday.
"In recent weeks, we have had a series of inhuman and despicable acts in different parts of the country that mark an irrational fight fundamentally between two existing criminal groups and their criminal allies," Mexican Interior Minister Alejandro Poire said.
There are "clear indications," he said, that a recent surge in violent acts -- including the mutilated remains found Sunday in Nuevo Leon state -- stem from a "direct conflict" between the Zetas and the Sinaloa cartels over territory and power.
Poire stressed that the Mexican government would not retreat from its efforts to crack down on organized crime, which is facing increasing criticism as Mexico's presidential campaign season heats up.
"I know very well that these acts worry society, but the solution is not to let our guard down," Poire said.
President Felipe Calderon, seen as the chief champion of Mexico's crime-fighting strategy, is not running for re-election. But opposition candidates have criticized his administration's approach.
More than 47,000 people have died in drug-related violence in Mexico since December 2006, when Calderon announced plans to deploy troops in efforts to combat cartels.
On Sunday, it appeared that authorities would be adding at least 49 more people to that tally, after decapitated and dismembered bodies were found along a highway in the municipality of Cadereyta Jimenez, near the industrial city of Monterrey and about 80 miles southwest of the U.S. border.
A message written on a wall nearby appeared to refer to the Zetas drug cartel.
The Zetas started with deserters from the Mexican army and quickly gained a reputation for ruthless violence as the armed branch of Mexico's Gulf cartel. The partnership ended in 2010.
Now, analysts say the Gulf cartel is allied with the Sinaloa cartel, one of the nation's most powerful drug-trafficking groups.
Sinaloa cartel leader Joaquin "El Chapo" Guzman Loera is widely known as Mexico's most wanted fugitive. Forbes magazine has placed him on its list of the world's most powerful people, reporting his net worth is $1 billion as of March.
Authorities are still working to identify the victims whose bodies were found Sunday, Poire said.
State officials said Sunday they had not ruled out the possibility that the victims could be Central American immigrants or residents of another state, telling reporters Sunday that there had not been many local missing persons reports in recent days.
But the area has become a battleground for a brutal conflict between the Zetas and the Gulf cartel, and reports of forced disappearances have become increasingly common in recent years.
So have claims that local police, with lower salaries that authorities say make them easier to corrupt than federal troops, have been infiltrated and influenced by cartels.
Last week, a retired military general arrived to take over Cadereyta Jimenez's depleted police force. At least five municipal employees were slain there last month, the state-run Notimex news agency reported.
Federal forces have stepped up security in Nuevo Leon and the neighboring state of Tamaulipas since November 2010. The states are among Mexico's most violent, according to government statistics.
In Monterrey, Nuevo Leon's capital, nearly 400 deaths in 2011 were connected to organized crime -- more than three times the number of people slain in drug-related violence there in 2010.
Among the most high-profile violence in the region was an attack on a casino in Monterrey last August that left 52 people dead. Authorities have said members of the Zetas cartel were behind that attack.
CNN's Catherine E. Shoichet, journalist Victor Badillo and CNNMexico.com contributed to this report.