US prosecutors identified a fourth person charged in a betting scheme involving an NBA player, saying the accused man had turned himself in.

Federal prosecutors in New York announced charges on Thursday against four people involved in conspiring to rig basketball games, but made only three names public: Timothy McCormack, Mahmud Mollah and Long Phi Pham, also known as "Bruce."

The name of a fourth man, Ammar Awawdeh, was revealed on Friday, with a US Attorney's Office representative saying in a statement that he had surrendered.

The charging document does not say which basketball player was involved in the scheme, but the NBA in April banned Toronto Raptors forward Jontay Porter for life after a bombshell probe found he bet on league matches.

US media has reported that Porter was the player who worked with the four men.

AFP confirmed the information by cross-referencing court filings, game statistics and the NBA's internal investigation into two games on January 26 and March 20.

According to the investigators, McCormack won $44,000 thanks to his bets, while Mollah netted over $1.2 million. 

The two are accused of getting Porter to leave two games for medical reasons after a few minutes of play so they could bet against him.

Alerted by online betting companies, the FBI began an investigation.

McCormack and Mollah were charged on Thursday and released on bail, while Pham was arrested on Monday at New York's JFK airport before he could board a one-way flight to Australia.

The NBA accuses Porter, the younger brother of Denver Nuggets star Michael Porter Jr., of placing at least 13 bets on NBA games from January through March of this year while traveling with either the Raptors or their G League affiliate Raptors 905.

NBA players are forbidden from wagering on NBA games under league rules. Those found to have gambled on NBA games risk a fine, suspension or life ban from the sport.

"There is nothing more important than protecting the integrity of NBA competition for our fans, our teams and everyone associated with our sport, which is why Jontay Porter's blatant violations of our gaming rules are being met with the most severe punishment," NBA Commissioner Adam Silver said in April announcing Porter's ban.

A majority of US states have legalized sports betting since a Supreme Court decision in 2018.