Former Nigerian oil Minister Diezani Alison-Madueke was arrested Friday in London on unknown charges by the U.K. National Crime Agency and granted bail the same day by a magistrate’s court in London, TheGuardian reports.

Alison-Madueke, 54, is the first female president of OPEC, elected in Vienna on Nov. 27, 2014.

She served as Nigeria’s oil minister — one of the most influential cabinet members of President Goodluck Jonathan’s administration — from 2010 until May 2015, AlJazeera reports. Jonathan was defeated by President Muhammadu Buhari in March. Alison-Madueke had been out of the country since Buhari took office, according to TheGuardian.

Alison-Madueke was one of five people arrested by the U.K. National Crime Agency.

There’s no information about the charges against Diezani Alison-Madueke, TheGuardian reported.

It is not clear whether she was arrested at the request of the Nigerian government. Buhari said in the last week that those who misappropriated billions of naira belonging to the Nigerian National Petroleum Corporation would soon be prosecuted, according to TheGuardian.

In a 27-word statement on its website, the U.K. National Crime Agency said it “arrested five people across London as part of an investigation into suspected bribery and money laundering offences.”

In Nigeria, the British High Commission also told news media that some arrests were made Friday, but did not identify those arrested.

Commission spokesman Joseph Abuku said, “This morning, five people between the ages of 21 and 60 were arrested on suspicion of bribery and corruption offences. The crimes are being investigated by the National Crime Agency.

The financial crimes unit sealed one of Alison-Madueke’s houses in the upscale Asokoro district of Abuja, two security officials said, according to AlJazeera.

Buhari has been criticizd for failing to appoint a cabinet or an economic team four months after taking office, according to AlJazeera. Getting tough on corruption could deflect criticism as Nigeria’s economy endures severe crisis due to the plunge in global oil prices.

Being a successful woman in a male-dominated sector is hard enough, but Alison-Madueke endured almost epic underdog status as Nigeria’s oil minister, according to an earlier AFKInsider report.

She was accused of mismanagement, corruption, and lack of transparency, ThisDayLive reported. Nothing ever came of these accusations until now.

In November 2014, Alison-Madueke blazed a new trail, going where no woman has been before when she was elected the first female president of OPEC, the Organisation of Petroleum Exporting Countries.

In 2008 she was investigated by the Nigerian Senate for paying $263 million to contractors while she was Transport Minister. She was never charged. Then she was accused of spending $20 billion dollars that went missing from oil coffers.

In September 2008 there was an unsuccessful attempt to kidnap her and her son. In October 2009, the Nigerian Senate indicted Alison-Madueke and recommended prosecution for the alleged transfer of 1.2 billion naira into the private account of a toll company. That went nowhere. She is accused of leaving Nigeria before her term as oil minister was up, allegedly to escape the new administration of President Buhari with his anti-corruption ticket.

She was deemed aloof, inaccessible and an absentee minister who was hardly at her desk, according to ThisDayLive.

“She was reviled and blamed for much of the ills – real and imagined – of the oil and gas sector,” the report said.

Not everyone was buying in to the attacks on Diezani Alison-Madueke’s character. She was featured on the cover of Forbes Magazine’s April-May edition.

As the new president of OPEC, Alison-Madueke took over from Abdourhman Atahar Al-Ahirish, Libya’s vice prime minister of corporations.

Alison-Madueke talked to CNBCAfrica about what it was like to break into new frontiers.

“When you realize the glass ceilings you’re breaking open a door or window for other women all over the world to enter, it brings with it great responsibility,” she said. “The gravity and burden of the responsibility is always on me as I break into new frontiers.

“As women, no matter how adept we may appear to be, there are many women around the world who have been shut out. We work probably more than our male counterparts to make sure we are fitting mentors for the women who come behind us — because they will come.”

Nigeria’s oil sector has been rife with theft and vandalism. It has been challenging, Alison-Madueke said, but the sector is a challenging one all over the world — not just in Nigeria.

So how did she handle the viciousness of her attackers?

“This is a challenging sector for a woman in a man’s world and I’m not feeble about it or shaken by the vagaries and viciousness that surrounds the politics of Nigeria,” she told CNBC in June. “Instead of turning around and being equally vicious, I put my energy in turning around the sector.”

She cited subsidy fraud. “In 2011 I cut off 92 marketers who we believed were carrying out illegal acts. Immediately the level of subsidies dropped by almost 50 percent. We went for complete deregulation shortly after that…to improve transparency,” she said.