Updated

Mexico detained a former senior police official Friday as it investigates alleged high-level corruption within security forces battling powerful drug cartels.

The announcement came on another day of extreme violence in Mexico. In the northeast, police mistakenly opened fire on a family of six, seriously wounding a teenage girl. In the west, inmates rioted, killing six. And police in Tijuana found three more bodies accompanied by messages that appeared to be from drug traffickers.

Rodolfo de la Guardia Garcia, the No. 2 official in the Federal Agency of Investigation from 2003-2005, has been placed under house arrest for 40 days as investigators look into the possibility he leaked information to the Sinaloa cartel in return for monthly payments in dollars.

De la Guardia also is listed on an Interpol Web site as a member of Interpol's executive committee in 2003, but the agency's officials in Paris were not immediately available to comment. Mexican authorities were checking his employment history.

Friday's announcement by the Attorney General's office was part of the Mexican government's "Operation Clean House," which aims to weed out corruption that came to light after the January arrest of Alfredo Beltran Leyva, a reputed Sinaloa cartel lieutenant.

Former federal police commissioner Gerardo Garay and three other officials of the Public Safety Department were arrested earlier, though officials have not revealed the allegations against them.

In the past two weeks, the Sinaloa cartel also has been linked to four Mexican military officers and one soldier, as well as five officials in the organized-crime unit of the Attorney General's Office, which oversees the agency that employed de la Guardia Garcia.

President Felipe Calderon has long acknowledged corruption among the federal police and soldiers leading Mexico's anti-drug campaign. These announcements suggest corruption still reaches high in the ranks of law enforcement despite decades of crackdowns.

The Sinaloa cartel is one of several criminal gangs waging a savage battle for control of lucrative routes used to bring illegal drugs to consumers in the United States. Hundreds of people have been killed, often decapitated, across northern and western Mexico. The death toll among police is particularly high, leaving officers fearful and jittery.

In the northern city of Monterrey on Friday, police mistakenly opened fire on a family of six after confusing their vehicle with a getaway car used by armed robbers. Among the wounded was a 13-year-old girl shot in the head and chest, said Nuevo Leon state Security Secretary Aldo Fasci Zuazua. Her father was shot in the shoulder and hand.

A bullet also grazed the mother's head. She was recovering at a hospital. A 2-year-old boy suffered minor injuries and two other children, 4 and 6, were treated for shock and released.

Enrique Maldonado, 33, and his wife Janeth, 31, were bringing their children home from a birthday party.

"They started raining us with bullets," Maldonado told the local TV station Multimedios. "We prayed to God because we didn't know what was going to happen to us."

Fasci Zuazua pledged to thoroughly investigate the shooting, which he called "an error in police procedure." He told Multimedios that he has asked to be removed from his position while the incident is investigated.

In other violence, six prisoners died and two inmates were injured in a riot early Friday in a prison in the Pacific resort city of Mazatlan, the Televisa television network reported. State authorities gained control of the prison shortly after the uprising. Mazatlan is in Sinaloa state, from which the Sinaloa cartel gets its name.

In the border city of Tijuana on Friday, three bodies were found alongside messages apparently from drug traffickers, Baja California's state attorney general's office said. Another man was found riddled with bullets hours later.

More than 4,000 people have been killed this year across Mexico as drug gangs lash back at Calderon's national crackdown on organized crime. More than 1,000 of those deaths have been in Ciudad Juarez, where on Thursday, the corpse of a beheaded man was hung from an overpass in a gruesome display.