Mexican authorities say homicide charges have not yet been filed in the June army killings of 22 people that a witness has described as a massacre.

Authorities announced last week that three soldiers would be prosecuted in the civil judicial system. Attorney General Jesus Murillo Karam said at the time that charges would be filed the next day.

Murillo said Monday they have not yet been formally accused.

He said there is no hurry since the suspects are in custody. He added that prosecutors want to present charges when they are at their "most profound and most serious."

The military initially said all 22 suspected gang members died in a fierce firefight June 30. A witness later told The Associated Press all but one surrendered before they were shot dead.