By BRIAN MAHONEY, AP Basketball Writer

David Stern led the NBA through drug problems and work stoppages. Now his league faces the stigma of a point-shaving scandal involving a referee.

The NBA acknowledged Friday that the FBI is investigating Tim Donaghy for betting on games, including ones in which he officiated.

According to a law enforcement official, authorities are examining whether the referee made calls to affect the point spread in games on which he or associates had wagered over the past two seasons.

The referee had a gambling problem and was approached by low-level mob associates through an acquaintance, said the official, who spoke to the AP on condition of anonymity.

Donaghy is perhaps best-known previously as one of the referees in the 2004 game at Detroit that ended with Indiana Pacers players fighting with Pistons fans, among the biggest black marks in league history.

This could top it.

"We would like to assure our fans that no amount of effort, time or personnel is being spared to assist in this investigation, to bring to justice an individual who has betrayed the most sacred trust in professional sports, and to take the necessary steps to protect against this ever happening again," Stern said in a statement.

Donaghy officiated 68 games in the 2005-06 season and 63 games in 2006-07, according to the Elias Sports Bureau. He also worked 20 playoff games, including five last season — Pistons-Magic on April 23; Warriors-Mavericks on April 27; Suns-Lakers on April 29; Nets-Raptors on May 4; and Spurs-Suns on May 12.

NEW YORK - Former referee Tim Donaghy pleaded guilty to two felony charges Wednesday in an NBA betting scandal that rocked the league and raised questions about the integrity of games.

Donaghy faces a maximum of 25 years in prison when he is sentenced for conspiracy to engage in wire fraud and transmitting wagering information through interstate commerce. He was released on a $250,000 bond.

Donaghy provided recommendations, called "picks," to co-conspirators about what team they should bet on, said U.S. District Court Judge Carol Bagley Amon. If he was correct, they paid him.

The picks included information about games that Donaghy officiated, the government said.

The information was not public, the judge said. Donaghy had "unique access," including what crews would officiate at games, the interaction of different officials and players, and the physical condition of certain players.

He concealed the scheme from the NBA and other referees to avoid detection, the judge said.

Donaghy also must pay a $500,000 fine and at least $30,000 in restitution.