GARCIA: Authorities arrested four police officers and six other suspects Thursday in the assassination of an army general who had been appointed police chief of this northern Mexican town over the weekend.

Brig. Gen. Juan Arturo Esparza was the latest military officer killed after taking over a Mexican municipal police force plagued with corruption. President Felipe Calderon has acknowledged that police forces throughout Mexico are rife with officers in the pay of cartels, and he has relied heavily on the military to fight drug trafficking.

The attack Wednesday had its origins in an illegal quarrying company, said Alejandro Garza y Garza, the Nuevo Leon state attorney general.

He said one of the suspects was facing investigation for operating the company and enlisted the help of a local hotel owner with ties to organized crime to intimidate officials in Garcia, a town outside the northern city of Monterrey.

Garza y Garza did not specify what criminal gang may have been involved, but Mexico's powerful drug cartels often control other illegal activities.

Some 30 gunmen arrived at the home of Mayor Jaime Rodriguez to give him a "scare" Wednesday, Garza y Garza said at a news conference. As the group was leaving, they crossed paths with Ezparza, who was driving to the mayor's home after hearing about the threat.

The gunmen sprayed Ezparza's car with bullets, killing him along two former soldiers and two municipal police officers escorting the general, Garza y Garza said. The mayor told reporters Wednesday he heard the gunshots from his home.

The operator of the quarrying company and the hotel owner were both arrested, along with four municipal police officers and four other civilians. Garza y Garza did not specify what role the police officiers and four civilians were believed to have played in the attack.

Earlier in the day, officials shuttered the local police station while state investigators questioned the entire Garcia police force about the killing.

State police moved in to temporarily replace the municipal force, and hundreds of soldiers were deployed to Garcia to reinforce security.

At the Garcia police headquarters, a sign on the door said all activity was suspended. Soldiers surrounded the building. Trucks of state police regularly circled the town hall. Two state troopers with machine guns guarded the driveway leading to the mayor's home.

"We're living in an atmosphere of unease and fear," said Jorge Tamayo, who was strolling the town plaza with his wife and 3-year-old daughter. "We feel that anything can happen to anyone."

Esparza was appointed police chief Saturday — part of a trend to name active or retired military officers to oversee municipal police forces. His appointment came months after some Garcia police officers were arrested for corruption.

Several of the military officers have been attacked. In April, an army colonel was killed less than three weeks after taking over the local police force in Piedras Negras, across the border from Eagle Pass, Texas. In August, an ex-general serving as chief in the northern city of Monclova survived an assassination attempt that killed three of his bodyguards.

Crackdowns on local police have become a common part of Mexico's drug war.

In June, nearly 80 police officers suspected of working with drug smugglers were arrested in 18 towns across Nuevo Leon — including some in Garcia — after soldiers found lists of policemen's names in the possession of traffickers.

Last week, federal Public Safety Secretary Genaro Garcia Luna proposed disbanding Mexico's 2,022 municipal police departments and combining them with state law enforcement agencies. He said local police have fewer resources to fight crime and their lower salaries make them more susceptible to corruption.

Nearly 90 percent of Mexico's municipal police forces have staffs of less than 100 people, according to a government report. More than 60 percent of local police receive monthly salaries of only 4,000 pesos (about $300). Most of them have completed less than 10 years of schooling and are either at basic education levels or illiterate, the report said.

In other violence Thursday, three bullet-ridden bodies were found in different towns around the Pacific coast state of Guerrero. The bodies all had their hands and feet tied and were found next to threatening messages. One was found along the highway connecting the resort towns of Acapulco and Zihuatanejo.