The Independent Corrupt Practices Commission (ICPC) said in a statement on Thursday that Gimba Yau Kumo and two others were being sought for misappropriating and diverting funds earmarked for a national housing project development.
Kumo, who married Buhari’s daughter Fatima in 2016, served as chief executive officer of a Nigerian mortgage bank and is under investigation along with Tarry Rufus and Bola Ogunsola.
Buhari, a former general, was first elected in 2015 promising to clean up Nigerian politics and make fighting corruption in Africa's largest economy one of his main targets.
But critics have in the past accused his government and Nigeria’s ruling elites of using the country's anti-graft agencies as political tools to target enemies.
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"The persons whose pictures appear above, Mr Tarry Ruffus, Mr Gimba Yau Kumo and Mr Bola Ogunsola, are hereby declared wanted... in connection with issues bordering on misappropriation of national housing funds and diversion of the sum of $65 million," the agency said.
It said anyone with information about their whereabouts should contact police.
Kumo and the other two individuals could not immediately be contacted for comment.
Buhari spokesman Garba Shehu confirmed the investigation into the president's son-in-law.
"It is an old case, its been going on for some time. He is the former managing director of the Federal Mortgage Bank," Shehu told AFP.
Africa's largest petroleum producer, Nigeria in 2020 ranked 149 out of 180 in Transparency International’s Corruption Perception Index.
When Buhari came to power he spoke of "mind-boggling" stealing by the previous government, but the looting of state funds has been going on for decades.
Billions of dollars were estimated to have been stolen by late Nigerian dictator Sani Abacha during his iron-fisted rule from 1993 and 1998.
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