The Nigerian government has admitted collaborating with the United Kingdom’s National Crime Agency, NCA, in the investigation of former oil minister, Diezani Alison-Madueke, for bribery and money laundering in London.

Alison-Madueke, who was arrested in the United Kingdom Friday along with four other unnamed people suspected to be her family members on allegations of money laundering, was later released and charged to court Monday.

“Nigeria is aware of the arrest of the former petroleum minister in London on money laundering charges,” presidential spokesman Garba Shehu told AFP.

“The government has been informed and the DSS (Department of State Services) is collaborating with the relevant security agencies in the UK to handle the matter,” he said.

The NCA said it had detained five people on suspicion of bribery and money laundering but later released them on bail. But the agency did not disclose the identities of the suspects.

“All five people arrested were released on conditional bail later that evening, pending further investigation both in the UK and overseas,” a statement issued by the agency said.

“The investigation commenced in 2013 under the Proceeds of Corruption act, and transferred to the NCA earlier this year.”

Nigeria’s Economic and Financial Crimes Commission, EFCC, refused to confirm the arrest but was reported to have sealed her home in Nigeria’s capital, Abuja.

Alison-Madueke aged 55 who was the first female petroleum minister in Nigeria — Africa’s largest producer — and the first female president of the global oil cartel OPEC, served under the immediate past administration of Goodluck Jonathan which left office in May.

She had previously been accused of large-scale fraud in the management of the country’s multi-billion-dollar oil wealth but denied any wrong-doing.

As far back in February 2014, the Nigerian National Petroleum Corporation, NNPC, then supervised by Alison-Maueke was accused of failing to remit to government coffers about $20 billion in revenue by the former governor of the Central Bank of Nigeria, CBN, Lamido Sanusi.