Updated

NBA Commissioner David Stern broke his silence Tuesday on the investigation into possible game fixing by suspected rogue referee Tim Donaghy, saying that as far as he knows the allegations represent an "isolated incident."

Federal investigators were examining whether Donaghy made calls to affect the point spread in games on which he or associates had wagered thousands of dollars over the past two seasons.

Authorities allege the referee had a gambling problem and was approached by low-level mob associates tied to the Gambino crime family to fix the scores of NBA games to pay off his debts.

"I understand Donaghy is the only referee to have allegedly bet on games and disclosed information to others," Stern said. "It is an isolated case. ... That's my current understanding, and I await the outcome of the investigation."

A somber Stern, addressing reporters in New York City, said he felt "betrayed by what happened on behalf of the sport."

"It is nothing but an act of betrayal," he said.

"We understand that he is accused of betting on games in the NBA," Stern said. "We're not positive it's games that he worked. ... I understand that he may have bet on other games in which he didn't work

"He will likely be accused of providing information to others for the purpose of allowing them to profit on betting of NBA games," he said. "I don't know the number of games; I don't know which games."

Stern added that his office was just beginning its investigation because it wanted to stay out of the way of federal authorities looking at the case.

"On July 9, Donaghy resigned," Stern said. "We would have liked to have terminated him earlier upon learning certain things."

The NBA already had a problem with Donaghy dating back to January 2005 relating to a domestic dispute with a neighbor, Stern said.

"It came to the NBA's attention [Donaghy] was involved in disputes with his neighbor that resulted in a filing of litigation," he said.

Donaghy told NBA investigators that he was the "victim" in the dispute, which Stern described as a harassment report. Stern said the league told Donaghy it was unhappy with the accusations, and the official subsequently moved to Florida.

Donaghy also was the subject of an earlier gambling allegation, Stern said.

"An allegation was made to our investigators ... suggesting that Donaghy had gambled at the Borgata Hotel in Atlantic City," he said. "We checked not only the Borgata but every casino in Atlantic City and Las Vegas ... all of our investigation came up negative," he said.

"No other allegations against him of any kind, no reports of any kind and the background checks that we do each year yielded nothing that raised any suspicions," Stern said.

"His on-court performance ranks him as a top-tier official ... a good ranking," he added.

Donaghy, meanwhile, told police in Florida that he feared for his life.

Three squad cars from the Manatee County Sheriff's Office arrived Sunday at Donaghy's home in Bradenton, Fla.

"Our concern is for his safety and his family's safety," Sheriff's Lt. Robert McNealy told the new York Post. "We are definitely going to share any information we get with the FBI."

The Donaghy family is even urging him to enter the federal witness-protection program, according to one friend interviewed in The New York Post.

"They think he will be killed if he goes to prison, or even if he doesn't, just because he's probably talking, cooperating, and that's ratting on the mob," the friend said. "I don't think [the Mafia] would take that very well.

The Associated Press contributed to this report.