Mr Fernandez de Cevallos has served as a senator and congressman
A former presidential candidate in Mexico has gone missing in suspicious circumstances, prosecutors have said.
The car of Diego Fernandez de Cevallos was found abandoned near his ranch in the central state of Queretaro amid "signs of violence", they added.
Local media have been giving conflicting reports of his fate.
Mr Fernandez de Cevallos was the 1994 presidential candidate of the governing National Action Party, but he continues to be an influential figure in Mexico.
The 69-year-old served as a senator and congressman while also pursuing a successful career as a lawyer, winning some of the country's biggest court judgments, often in suits against government agencies.
Mr Fernandez de Cevallos finished second to Ernesto Zedillo in 1994.
The BBC's Inma Gil in Mexico City says the disappearance of the man known as "Diego the boss" has sparked all sorts of speculation in a country ravaged by drug related violence.
Some local media reported he had been kidnapped, others that he had been killed.
The federal attorney general's office said it could not confirm any of the reports.
Correspondents say kidnapping is rife in Mexico, which is in the grip of a battle between the security forces and drug cartels that has left 23,000 people dead since President Felipe Calderon's election in 2006.
Separately, Mexican authorities said an armed gang killed eight people and injured at least 12 in a bar in the town of Torreon in the northern state of Coahuila on Saturday morning.