The protesting federal police are demonstrating against a plan that dissolves the force and incorporates it into the Guard, which has now been deployed to seal the country's porous southern border and control immigration and crime.
President Andrés Manuel López Obrador, who took office Dec. 1, attributed the protests that erupted Wednesday to "dark forces" and suggested there were ulterior motives, without explaining his accusation. Security secretary Alfonso Durazo went further Thursday, suggesting former President Felipe Calderón was among those responsible.
"Some of the visible leaders of the movement are not members of the institution," Durazo said. "They are people tied to interest groups who have profited from million (peso) contracts for the purchase of unused gasoline and technology among many others."
Calderón, who narrowly defeated López Obrador in the 2006 presidential election and was president in 2006-2012, denied he was behind the protests.
"The federal police protests have underlying causes (labor issues) and in the manner" with which the López Obrador administration has spoken of the federal police, Calderón wrote. "I reject the cowardly insinuation that I am behind this."
Durazo criticized some of those now defending the federal police, including Calderón, saying that when in the government they did not develop the federal police as an effective security force.
"If the federal police was a sufficient and adequate entity we wouldn't have the levels of insecurity that we have today," he said.
He also accepted some responsibility for the protest, saying that communication may have been insufficient as the government rushed to do away with the agency.
In response to concerns that police would lose their seniority or be out of a job if they didn't join the Guard, he said no one would be fired or have their benefits eliminated.
He also rejected any suggestion that National Guard members seen near the striking police were intending to provoke them.
Still, police continued to dissent as protests stretched on.
Officer Julio Nueva Rios said López Obrador had characterized the federal police as contaminated, corrupt and inefficient and urged others around Mexico to join the strike.
"They want to turn us into soldiers when we're police," he said.
He also denied the suggestion that police had been manipulated by political forces.
"We're purely federal police," he said. "There's no politician. There's no party."
Mexico is experiencing the highest number of killings in at least 20 years, though the rate of the homicides has stabilized in recent months.
Associated Press journalist Jorge Barrera in Mexico City contributed to this report.