Prosecutors in Mexico have formally charged three generals and a lieutenant-colonel with having links to a drug-trafficking gang.
Gen Roberto Dawe Gonzalez, and retired officers Tomas Angeles Dauahare, Ricardo Escorcia Vargas and Silvio Hernandez Soto, were arrested in May.
They are accused of ties to the Beltran Leyva cartel - charges they deny.
The men are among the highest-ranking officers to be arrested and charged in recent years.
Mexican troops have played a key role in tackling the drug gangs over the past six years.
Charges of "organised crime to further drug-trafficking" have been brought against the four men, according to a statement from the Attorney General's Office.
The statement gave no further details but correspondents say they are suspected of supporting or protecting the Beltran Leyva gang.
Gen Angeles was assistant defence minister from 2006 to 2008, when he retired.
Gen Escorcia was the head of the military in Morelos state that was considered Beltran Leyva territory. He stepped down in 2010 when he reached retirement age.
Gen Dawe commanded a military base in western Colima state, an important trafficking route.
Lt-Col Hernandez Soto retired from the army in 2002 and became a senior police commander in Sinaloa state.
Prosecutors have also lodged charges in the same case against US-born Edgar Valdez, alias "Barbie", who is accused of trafficking and murder.
Mr Valdez, who was arrested in 2010 and confessed on video to working in the drugs trade, is said to have risen to prominence as the security guard of cartel leader Arturo Beltran Leyva.
The gang began to fragment in 2009 after Beltran Leyva was killed in a shootout with marines.
Mexico's drug cartels have been under systematic attack since President Felipe Calderon deployed troops against them six years ago.
Drug-related violence since then has killed more than 50,000 people.