Not so long ago, FBI agents probing the activities of poker websites they believed to be illegally operating in the US identified nine wire transfers of about $400,000 – a total of $3.6m (£2.2m). They were made to a discreet branch of Barclays near Harrods in Knightsbridge that is dedicated to wealthier clients.

They were just a sample of hundreds of payments to scores of accounts to have come onto the FBI's radar. Investigators have for years been tracking the activities of a number of sites active in the US, where online gambling is effectively illegal. Looming large in their sights have been PokerStars and Full Tilt Poker: the Google and Facebook of online gambling, thought to service over half the global player base between them.

Several bank accounts in the US, the FBI believes, can be shown to be linked to gambling activities, but many more payments have gone further afield – to Canada, Switzerland, Cyprus, Panama, Hong Kong, Malta, Andorra, the Philippines, Luxembourg, Ireland and Jersey.

Two months ago, officials arrested four of the 11 men now facing multibillion-dollar gambling, bank fraud and money laundering charges. The US department of justice (DoJ) has frozen many accounts around the world.

The transfers to Barclays are thought to have left the account before the DoJ could freeze it, but investigators were drawn by payment references such as "FFC [for further credit] … Chad Elie" and "FFC … Chad Canary" – both believed to refer to one of the FBI's main suspects.

Chad Elie, a flamboyant 31-year-old Las Vegas-based businessman, is one of four people accused of helping online poker firms disguise the movements of funds between players' US bank accounts and offshore websites. Such payments were outlawed by the 2006 Unlawful Internet Gambling Enforcement Act but, claims the DoJ, Elie has been among the most adept at finding ways to disguise these money flows.

It is claimed that he has been paid handsomely for his efforts in assisting PokerStars, Full Tilt and others. Among the cover stories he is alleged to have helped create is fictional payday loan activity through a series of accounts.

More audacious still, claims the DoJ, was another ruse: he and associates are alleged to have persuaded a small number of local US banks facing financial difficulties to wave through poker money flows without raising the alarm. In exchange, the banks are said to have received huge fees as well as promises of multimillion-dollar investments.

In one example, over a period of 11 months last year, a bank in which Elie and a partner had invested millions is alleged to have processed $200m in payments for PokerStars and Full Tilt before the regulator stepped in.

The day after his dramatic arrest two months ago, Elie was determined to show prosecutors his best poker face. After pleading not guilty to nine charges for which he could face years in jail, he celebrated his release on $250,000 bail by going ahead with his wedding to former Playboy playmate Destiny Davis.

Also arrested at around the same time as Elie was Bradley Franzen, another entrepreneur allegedly used by PokerStars and Full Tilt to find ways of masking payments. Based in Illinois, he ran a business out of Costa Rica. Among the schemes in which he is said to have been involved was setting up a phoney business called Green2YourGreen. Several US banks were told this was a sales business that allowed consumers to buy environmentally friendly household products and sell them to other consumers. The site is said to have echoed similarly phoney retailers set up to hide poker payments, including sites selling golf clubs, watches, bicycles, jewellery, clothing, or even settling medical bills.

After initially protesting his innocence, six weeks ago Franzen changed his mind, reaching a plea bargain deal with prosecutors. And with his plea came another revelation: after years of struggling to keep its payment arrangements one step ahead of the US authorities, Franzen claimed, Full Tilt was now hiding a $60m black hole in its supposedly ringfenced player accounts.

Panic quickly spread among players around the world, with Full Tilt's US customers launching a $150m class action. Meanwhile, on Alderney in the Channel Islands, where the site is licensed, the local regulator removed from its own website a statement saying: "There is no reason to believe player fund transactions are fundamentally threatened by any consequence of the US authorities' actions." Two weeks ago, it also formally withdrew Full Tilt's licence and the firm was forced to cease trading, leaving players uncertain about whether they will ever get their money back.

Rumours are circulating of a white-knight bidder emerging to rescue Full Tilt outside the US, but that almost certainly depends on an agreement being reached with the DoJ and could also require a sizeable investment.

Meanwhile, the company's fate should look clearer following a public hearing convened by the Alderney authorities in south London later this month. The regulator may judge the DoJ to be holding aces. This might be a hand to fold.

Around the table

Preet Bharara, nominated as US Attorney for the Southern District of New York by President Obama two years ago, is leading the latest US crackdown on online poker operators. He has built a formidable reputation, having been involved in Madoff prosecutions as well as securing a string of convictions relating to the Gambino crime family. Most recently he led a successful offensive against insider dealing – including the conviction of former hedge fund boss Raj Rajaratnam – that led to him being labelled the Sheriff of Wall Street. Born in India, he grew up in New Jersey and went on to Harvard and Columbia Law School.

Ray Bitar, a 39-year-old former Los Angeles equities trader, gave up stock-picking to found Full Tilt in 2004. He built the poker brand around star poker players such as Howard Lederer and Phil Ivey, offering them an interest in the business. In April, the DoJ moved to seize his four homes in California and many bank accounts in his name around the world. He still has houses in Ireland and Bermuda. Tall and overweight, with a dark goatee, Bitar spends much of his time in Ireland, where much of his staff are based on a business park just south of Dublin.

Isai Scheinberg, an Israeli-Canadian poker enthusiast who worked for IBM as a programmer for many years, founded PokerStars 10 years ago. Within five years it became the world's largest poker site after deciding to continue servicing US players despite new anti-gambling laws, which triggered an exodus of rivals. He has homes in Toronto and the Isle of Man.