Ehud Olmert is facing a third investigation into criminal allegations.
Israel Attorney General Menachem Mazuz on Sunday instructed police investigators to open a probe into whether the prime minister, as trade and industry minister between 2003 and 2005, helped a former business partner gain from a state investment center and illicitly appointed cronies to government posts.
Olmert already is being investigated on suspicion of bid rigging in the 2005 privatization of an Israeli bank , as well as on allegations that a discount on a Jerusalem home he bought in 2004 constituted bribery.
The prime minister has denied wrongdoing in all of the cases. Olmert has accused some state officials of conducting a witch hunt against him.