GBAM! Patience Jonathan Is Planning To Sue EFCC For Investigating Her - BBC
But the Economic and Financial Crimes Commission (EFCC) refused to confirm whether it had blocked any of her funds.
A letter from her lawyers, published in several Nigerian newspapers, alleges that $15m (£11.4m) was blocked in July – and that the money is for the former first lady to settle medical bills abroad.
Her lawyers, Granville Abibo (SAN) and Co, told the BBC the firm had written to the EFCC on her behalf but refused to give further information.
Muhammadu Buhari won elections last year, when he beat former President Goodluck Jonathan, promising to fight corruption.
Several top former military officers and politicians are currently being prosecuted for corruption.