"The head of government has been asked to provide explanations in connection with suspicions of fraud and other offenses," Israel's police and Justice Ministry said in a statement after questioning Olmert.
The new probe is apparently unconnected with a scandalous affair involving hundreds of thousands of dollars Olmert allegedly received over 15 years in cash-stuffed envelopes from American Jewish businessman Morris Talansky.
The new suspicions focus on Olmert allegedly asking several bodies to pay for official trips to other countries and receiving multiple sums for the same trips. He is accused of using the extra funds on private trips for himself and his family.
Olmert has been linked with several corruption investigations. He has denied all wrongdoing and vowed to resign should he be indicted.
All the cases are believed to have taken place before Olmert became prime minister in 2006.