Ruja Ignatova, also known as the "missing Cryptoqueen", has been placed on the FBI's top 10 most wanted list.

The Bulgarian woman, believed to be in her 40s, is wanted for her alleged role in running a cryptocurrency scam known as OneCoin.

Federal investigators accuse the fugitive of using the scheme to defraud victims out of more than $4bn (£3.2bn).

She has been missing since 2017 when US officials signed an arrest warrant and investigators began closing in on her.

In 2014, OneCoin, a self-described cryptocurrency, began offering buyers commission if they sold the currency on to more people.

But FBI agents say OneCoin was worthless and was never safeguarded by the blockchain technology used by other cryptocurrencies.

According to allegations made by federal prosecutors, it was essentially a Ponzi scheme disguised as a cryptocurrency.

A bureau notice published on Thursday offered a $100,000 reward for any information leading to the arrest of Ms Ignatova, who was charged in 2019 with eight counts

The FBI adds fugitives to its most wanted list when it believes the general public may be able to assist in tracking them down. She is the only woman on the FBI's 10 most wanted list.