Mexican prosecutors say they are investigating possible official involvement in last month's killing of the brother of former President Carlos Salinas.
But State Attorney General Alfonso Navarrete told reporters in Toluca Wednesday that there is no proof to support media speculation that members of the federal police could be involved.
Enrique Salinas was found dead in a car outside Mexico City with a plastic bag over his head. Authorities believe his death was connected to a failed extortion attempt.
His brother, Carlos Salinas, served as Mexico's president from 1988 to 1994. The former president lived in exile for years after he was widely blamed for a financial crisis that began shortly after he left power.
Another brother, Raul Salinas, is in jail for masterminding the 1994 murder of his former brother-in-law, prominent politician Jose Francisco Ruiz Massieu.
Some information for this report provided by AP and Reuters.