Kidnappers free mother of Nigerian minister

The mother of Nigeria's Finance Minister Ngozi Okonjo-Iweala has been released by her kidnappers, five days after she was seized from her home, Nigerian police said Friday.

Kamene Okonjo is well and in good health, police spokesman Frank Mba told CNN.

"The Okonjo Family is full of thanks to the Almighty for this happy development," a finance ministry spokesman said in a statement.

Okonjo, an academic who is reportedly in her 80s, was abducted on Sunday from her home in Ogwashi-Uku, in Delta State.

The kidnapping sparked what officials described as "a massive manhunt."

It remains unclear who her abductors were or whether their motive was financial or political.

The U.S. State Department warns U.S. citizens against travel to Delta State, among others, because of the risk of kidnappings, robberies, and other armed attacks.

Okonjo-Iweala has sought to push through reforms and tackle corruption while in office.

She lost her bid in April to become the next president of the World Bank -- the first ever challenge to the U.S. nominee in the institution's history.