Mexican soldiers arrested 13 alleged drug cartel members, including one man who had just arrived on a private plane to take over trafficking operations in the northern city of Monterrey, the Defense Department said.

Acting on a tip, soldiers arrested Rodolfo Lopez and several others Monday after they landed at Monterrey's international airport, the department said in a statement. Several armed men were arrested in the parking lot, where they were waiting to pick Lopez up, it added.

The department said Lopez had been chosen to take over trafficking operations for the cartel in the industrial city from Hector Huerta, who was captured March 24, one day after the government listed him among its 37 most-wanted smugglers. Lopez had not been on the list.

The department said Lopez told soldiers he had arrived from the Pacific resort town of Acapulco, where he received instructions about his new duties from cartel leader Arturo Beltran Leyva.

Four of the 13 suspects were arrested at a Monterrey residence. Soldiers seized 14 guns, a grenade, ammunition, drugs and cash during the operation.

They also found a banner with a message for the Mexican president, reading: "Felipe Calderon, please don't mess with the family because it is very sacred. Show respect or face the consequences of our people. They are tired of atrocities."

Police in southern Mexico, meanwhile, said they arrested a gang of at least six Gulf cartel assassins, including two women, who were allegedly commanded by top police officers.

The police chief, two commanders and a former public safety director in the city of Tapachula, near the Guatemala border, were also detained on suspicion of leading the hit gang.

The suspects allegedly worked for the Zetas, a gang of enforcers linked to the Gulf cartel. Police and soldiers seized dozens of grenades and assault rifles during the weekend raid in which the alleged assassins were captured, state prosecutors said.

Drug corruption scandals have blossomed across Mexico recently — in states far from the U.S. border region, where the drug battles have long been concentrated.

In Morelos, just outside Mexico City, prosecutors announced that the top state security official and the police chief in the state capital, Cuernavaca, were ordered held for 40 days on suspicion of aiding the Beltran Leyva cartel. Two other people were also ordered held in the case.

Meanwhile a prominent senator from Zacatecas state called a news conference to deny any knowledge of a large load of marijuana found earlier this year at a warehouse belonging to his brother.

On Jan. 22, army troops acting on a tip raided the brother's chili-drying warehouse and found people loading marijuana onto trucks. More than 11.4 tons of the drug were seized at the plant, near the city of Fresnillo.

"My brother said the (locks) had been broken, and he reported it to police," Sen. Ricardo Monreal told reporters Monday in Mexico City. The brother, Candido Monreal, has not been charged in the case.

The senator accused the Zacatecas government of being completely infiltrated by traffickers, and said he has resigned from the leftist Democratic Revolution Party, which governs the state, to protest what he called a smear campaign against him.

Government officials did not immediately respond to requests for comment.

Zacatecas is the same state where armed men staged a bold raid on a prison over the weekend that freed 53 suspects, dozens of them linked to the Gulf cartel.

Gov. Amalia Garcia said Saturday that prison guards were likely complicit. On Monday, she asked the state director of prisons to resign and cooperate with the investigation, according to a statement from her office.

Also Monday, police in the southern state of Guerrero found the severed heads of three men in an ice chest left on the side of a highway near the resort of Zihuatanejo. The cooler was wrapped in tape and a message was attached, but police did not reveal what it said.

The men's decapitated bodies were found about a mile away in an abandoned taxi, the state Public Safety department said. Some of the bodies had their hands bound behind their backs and showed signs of torture.

More than 10,750 people have been killed in drug violence during the past 2 1/2 years.