NEW YORK - NBA Commissioner David Stern said on Tuesday an FBI probe learned that former referee Tim Donaghy was a "rogue, isolated criminal" who bet on games and that it appeared no other league employees were involved.

NBA Commissioner David Stern speaks a press conference to discuss former NBA referee Tim Donaghy in New York July 24, 2007. Donaghy is accused of betting on games he officiated. [Reuters]

Stern told a news conference that he was told by the FBI, which is conducting the investigation, that Donaghy was the only referee it has evidence of betting on games.

"If that understanding changes tomorrow I will inform you," said Stern.

Stern vowed that the league would give its full cooperation and conduct an exhaustive review of its security practices.

"This is the worst thing that can happen to a professional sports league," said Stern, adding that any official's involvement in gambling shatters the covenant with fans over the integrity of the game.

"This is the worst situation I have ever experienced either as a fan of the NBA, a lawyer for the NBA or the commissioner of the NBA," he said, calling it "a betrayal of what we know in sports as a sacred trust."

Stern said the investigation involved games that Donaghy, a 13-year NBA veteran, worked over the last two seasons. Donaghy submitted his resignation on July 9.

The commissioner said the FBI came to him about Donaghy on June 20 and asked that the league not act on the information to safeguard the investigation.

Stern said the NBA has had talks with Donaghy's lawyer and understood he was discussing a plea deal with authorities.

Word of the FBI investigation broke Friday with a report that the referee's gambling became known during a separate investigation of organized crime.

"It is my understanding that he is accused of betting on games in the NBA," Stern said Tuesday about Donaghy, who he described as "a rogue, isolated criminal."

"Including some games that he worked and others he didn't work. I understand he will likely be accused of providing information to others for the purpose of betting on NBA games."

The commissioner said the NBA would review Donaghy's games after the criminal investigation is completed.

"He worked 150 games over the last two years ... we did not want to sort of march people together and say, we are now going to investigate Tim Donaghy ...

"But I can assure you that in the fullness of the summer and the autumn, we will have the opportunity to review Mr. Donaghy statistically and by video, and it will be done."

Stern said all gambling, other than off-season visits to horse racing tracks, was forbidden for officials. He said Donaghy earned $260,000 last season.

Asked if he was surprised by the breach, Stern said: "Yes, I'm surprised, but I think no more surprised than the head of the FBI, the head of the CIA, that rogue employees turn on their country in criminal activity despite the best investigative procedures you can possibly imagine."

Stern said the NBA routinely monitors officials, employing 30 observers to ensure one at every game. Every game is also reviewed on video and some are audited by a group supervisor.

Stern said the league hired additional experts this year to audit the auditors evaluating referees.

He said he expected changes in the wake of the scandal.

"We're going to revisit everything. Everything."