US authorities announced several high-profile arrests on Thursday, including of a star player and a coach in the National Basketball Association (NBA), for alleged illegal sports betting.

Among those in custody are Portland Trail Blazers coach Chauncey Billups and Miami Heat player Terry Rozier, both of whom were reportedly arrested after their teams' games on Wednesday.

The arrests are part of a sweeping investigation into illegal gambling that produced two indictments, the FBI said — one into players who are allegedly faking injuries to influence betting odds, and another involving an illegal poker ring tied to organised crime.

Here is what we know about the cases.

What are the allegations?

FBI Director Kash Patel described the allegations to reporters as 'mind-boggling'. They include indictments in two major cases, officials said, both involving fraud.

The first case is called 'operation nothing but bet,' in which players and associates allegedly used insider information to manipulate wagers on major sports betting platforms. In some cases, players altered their performance or took themselves out of games to ensure those bets were paid out, according to New York City Police Commissioner Jessica Tisch. Those bets amounted to tens of thousands of dollars in profits.

The second case is more complex in nature, involving four of the five major crime families in New York as well as professional athletes. The accused in that case are alleged to have participated in a scheme to rig illegal poker games and steal millions of dollars.

Authorities said they began probing these poker games in 2019, spanning multiple locations including the Hamptons, Las Vegas, Miami, and Manhattan. The accused allegedly laundered profits via bank wires and cryptocurrencies.

Which players have been arrested?

All in all, authorities say 34 defendants were indicted on charges related to the two fraud cases.

Six were charged in the first case of players allegedly faking injuries to influence betting odds, including Miami Heat player Rozier. Former NBA player Damon Jones was also arrested, said to be involved in two games that were part of the scheme.

The second case related to illegal poker games involved a total of 31 defendants, including Portland Trail Blazers coach Billups. Authorities stated that three of the accused were charged in both cases, as well as thirteen members and associates of the Bonanno, Genovese and Gambino crime families in New York.

What has the NBA said about the allegations?

In a statement, the NBA said it is in the process of reviewing the federal indictments and is cooperating with authorities. Rozier and Billups are being placed 'on immediate leave' from their teams. The league emphasized that the integrity of the game remains a top priority.

Who are New York's notorious 'Five Families'?

The alleged scheme involved four of the five well-known crime families of New York, which have ruled the city's Italian American mafia since 1931. While major takedowns in the 1990s reduced mafia activity, Thursday's indictments show that the mafia has not entirely disappeared, as the alleged organized crime operations persisted.