Nigerian former oil minister Diezani Alison-Madueke, who is under investigation over allegations of bribery and money laundering, has breast cancer and will undergo surgery in Britain, her lawyer said according to Reuters.

Nigerian authorities said Alison-Madueke, who served as oil minister for Africa’s biggest crude producer from 2010-2015, was arrested in London last week. Her lawyer, Oscar M. Onwudiwe, denied this, saying she spent only 45 minutes with police.

“Mrs Alison-Madueke was never arrested or detained and her passport was never seized. She was merely invited (by British police), and she honoured it promptly,” he said in a statement.

“The family … would plead with all reasonable Nigerians to pray for her recovery so that she can face these allegations and give account of her stewardship,” the lawyer said AP reported.

The ex-minister has been in London for months since her party lost power and President Muhammadu Buhari took office in May promising to halt endemic corruption. Nigeria’s former Central Bank governor has alleged $20b in oil sales went missing in two years under Alison-Madueke’s watch.

The lawyer denied allegations of corruption and media reports of the Madueke family’s ownership of multimillion-dollar homes in Britain and US denouncing “a deliberate and vicious campaign to demonize members of the Madueke family.”