Lagos - The family of the former oil minister is asking Nigerians to pray for her as she fights cancer and British allegations of corruption.
A statement from Diezani Alison-Madueke's lawyer denies she was arrested and says she was "merely invited" to answer questions by Britain's National Crime Agency last week.
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The agency confirmed only that it briefly arrested five unidentified people in a bribery and money-laundering investigation.
Nigerian newspapers reported Alison-Madueke had been arrested and released on bail.
Nigeria's former Central Bank governor has alleged $20 billion in oil sales went missing in two years under Alison-Madueke's watch.
Lawyer Oscar M. Onwudiwe said Friday the family asks for Nigerians' prayers as the ex-minister undergoes surgery next week after months of chemotherapy and hopes to emerge strong enough to confront the allegations.