By Claire Marshall
BBC, Mexico City
The 1971 shooting of students by government forces in Mexico's so-called "dirty war" has been classified by an investigating prosecutor as genocide.
President Fox appointed a special "dirty war" investigator
He presented his findings after a two-year investigation into the period.
A judge has to decide by Saturday if former President Luis Echeverria and a number of senior ex-government figures will face criminal charges.
The "dirty war" between government forces and leftist guerrillas took place in the 1960s and 1970s.
Mexico's special prosecutor is seeking scalps at the highest level for what he has called genocide.
At a news conference, Ignacio Carrillo concluded that the 1971 killing of student protesters by government forces in Mexico City amounted to this crime under Mexican law.
It is still not known how many died in the shooting, but the prosecutor put the number at dozens.
While Mr Carrillo refused to give any names, a news agency reports that he is seeking the arrest of Mr Echeverria and at least 10 other top officials.
Mr Echeverria could be the first Mexican president ever to face criminal charges.
However, given that the former leader is now 82, he would most likely be placed under house arrest.
Mr Carrillo's conclusions from his investigations into alleged crimes carried out during the "dirty war" have provoked a furious response from the Institutional Revolutionary Party, or PRI, which governed during that time.
However, President Vicente Fox has earned respect from many quarters for allowing the inquiry to continue.
One analyst told the BBC that "this shows that the tradition of impunity is being shattered and that no-one is outside the law".