Former Adamawa state governor Murtala Nyako (left) presents a staff to a tribal leader in Numan, Adamawa, Dec. 7, 2013. Reuters

The former governor of Nigeria's Adamawa state, Murtala Nyako, has turned himself in for questioning amid allegations of money laundering, a spokesman said Tuesday. Nyako, 72, was impeached by lawmakers in the northeast state last year after he resigned from the then-ruling Peoples Democratic Party to join the All Progressives Congress party that swept the nation's presidential and local elections in recent months.

Nyako is being investigated by the Economic and Financial Crimes Commission. "He reported [Monday] in our office for questioning. He was allowed to go home around 6:30 p.m. [18:30 GMT]. The interrogation continues [Tuesday]," EFCC spokesman Wilson Uwujaren told Agence France-Presse. His interrogation "has to do with financial transactions when he was governor of Adamawa state" from 2008 to his July 2014 impeachment, Uwujaren said.

Nyako's son, Abdul Aziz Murtala Nyako, a retired naval officer, is also wanted for alleged criminal conspiracy, stealing, abuse of office and money laundering.

Nigeria is Africa's most populous country and top economy. Newly elected President Muhammadu Buhari has vowed to wipe out government corruption. He took office last week.

The EFCC has been criticized in recent years for failing to secure high-profile convictions.