After allegedly conning British pensioners out of $70 million (£35 million), Zibiah Gunter, 25, had no reason to suspect that her world was about to come crashing down.

“CutiePie is going to have a nice day,” she enthused on her web page on Thursday. Alongside was a note: “Mood: happy.”

Hours later Ms Gunter’s sunny outlook probably changed when she was visited by special agents from US Immigration and Customs Enforcement (ICE), who arrested her after a joint investigation with the US Secret Service, US Attorney’s Office and City of London Police.

Her father, Paul, thought to be from Hertfordshire, was also arrested on Thursday in Tampa, Florida. Each now faces a prison sentence of up to 95 years and fines of up to $140 million.

Last night investigators in America and Britain were continuing to look for the money that the pair allegedly conned from more than 15,000 British pensioners. British officers believe that much of it has been salted away in Caribbean bank accounts, property in America and England and luxury items such as expensive cars. But some was reinvested in the scam, upgrading equipment and websites and recruiting more workers.

A senior police source told The Times: “They were making a lot of money but they didn’t just take the money and run. They . . . realised they [were] on to a good thing.”

It is claimed that Ms Gunter and her father hijacked the identities of at least 54 dormant publicly traded companies, then sold bogus shares to pensioners in Britain. Before embarking on the allegedly fraudulent scheme, Ms Gunter, who is British but holds a US passport, spent several weeks teaching English to children in the Dominican Republic.

Since at least spring 2005 the Gunters used “high-pressure and misleading sales techniques” to get investors to wire money to Florida banks, then used the money “for their own personal enrichment,” according to ICE. Neither has any previous criminal record.

According to the criminal complaint, the Gunters have been charged with conspiring to commit and committing substantive acts of mail fraud, wire fraud, securities fraud and money laundering. They are due to appear in court in Tampa on Monday.

British detectives expect to make more arrests for money laundering and other fraud offences.

The father and daughter team are alleged to have recruited financial advisers in England and taken them to Spain to make their calls. Once there they were told not to use their real names and many left after realising they were involved in a scam. Some are said to have been threatened.

It has taken City of London Police months to investigate the huge pyramid of people believed to be involved. Robert Wishart, deputy chief inspector and head of the money-laundering unit at the City of London Police, said: “They have been carrying out this scam for a couple of years at least and they made a lot of money out of it.”

According to a sworn statement by Anthony Magos, an agent with the US Secret Service, City of London Police were looking at the Gunters as part of their Operation Archway investigation into so-called boiler-room fraud, the name stemming from the high-pressure sales tactics employed by fake stockbrokers.

Their names came up after an American private investigator advised the Secret Service of a possible stock fraud involving more than $250,000 belonging to a British client who had tried to buy shares in several US companies that turned out to be bogus, including one called MobileStream.

Police in London established that many calls to UK investors recommending shares in MobileStream came from “boiler rooms” in Spanish premises owned by the Gunters. Detectives from the Norfolk Constabulary, acting on behalf of the UK’s Serious Fraud Office, arrested Mr Gunter in April but subsequently let him go. Officers of the ICE identified dozens of bank accounts to which the Gunters were signatories and which received money from UK investors.

ICE alleges that most of the proceeds were directed into two private companies that have substantial property holdings in central Florida.

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