MEXICO CITY (AP) — Mexican prosecutors formally filed drug charges Tuesday against four high-ranking army officers, including three generals and a lieutenant colonel.

They are the highest-ranking Mexican army officials arrested in at least 15 years, and allegedly provided protection for the Beltran-Leyva drug cartel. They were detained in May and have been held under a form of house arrest.

The Attorney General's Office said charges of "organized crime to further drug trafficking" were lodged against retired generals Tomas Angeles Dauahare and Ricardo Escorcia, as well as active service Gen. Roberto Dawe Gonzalez. Retired Lt. Col. Silvio Hernandez Soto faces the same charge.

The office did not mention specifics of the case lodged against the four along with an army major. But charged in the same case is U.S.-born drug trafficker Edgar Valdes Villarreal, alias "La Barbie," who worked for the Beltran Leyva cartel until it began to break up with the death of leader Arturo Beltran Leyva in a 2009 shootout with marines.

The investigation against them the officers is based on a case from 2009, the Attorney General's Office said.

The previous highest-ranking army official arrested was Gen. Jesus Gutierrez Rebollo, then head of Mexico's anti-drug agency, who was arrested in 1997 and later convicted of aiding deceased drug lord Amado Carrillo Fuentes.

President Felipe Calderon named Angeles Dauahare as assistant defense secretary in 2006. He left the post in 2008, when he retired.

Dawe Gonzalez was assigned to a military base in the western state of Colima.

Escorcia retired from active service in 2010 after reaching mandatory retirement age, but previously served as head of the military base in Cuernavaca, a city just south of the Mexican capital that has been considered Beltran Leyva territory.

Arturo Beltran Leyva was killed in a shootout at an apartment complex in Cuernavaca in 2009. Mexico's marines were reportedly called in to look for the capo after its army appeared to be slow to act on U.S. intelligence indicating the drug lord's location, according to a leaked U.S. Embassy diplomatic cable from late 2009.

Angeles Dauahare's lawyer, Alejandro Ortega, said the general told his wife shortly after his arrest that he is being accused of taking money from associates of Valdez Villareal, who was allegedly top hit man for Beltran Leyva. Valdez Villareal was arrested in 2010.

Ortega said his client denies the charges, and supports himself with an army pension and a house and an apartment he owns. He said the general's wife also owns a house she inherited.

A few senior military officers have been arrested for alleged links to traffickers during Mexico's long struggle to control the cartels.

Retired Gen. Juan Manuel Barragan Espinosa was detained in February for alleged links to organized crime and Gen. Manuel Moreno Avina and 29 soldiers who were under his command in the town of Ojinaga, across the border from Presidio, Texas, are being tried on charges of torture, homicide, drug trafficking and other crimes.

More than 47,000 people have been killed in drug violence since Calderon deployed thousands of soldiers to drug hotspots, according to government figures.

Also Tuesday, Mexico's Navy reported it had killed six suspected members of the Zetas cartel in the Gulf coast state of Veracruz. The Navy said its personnel was raiding a suspected cartel house when men armed with assault rifles and grenades emerged, and engaged Navy ground forces. Five other suspects were detained.