* Sterling has not issued statement over alleged comments
* Several companies have pulled sponsorship of Clippers (Updates with more sponsors pulling out and family's reaction)
April 28 (Reuters) - The National Basketball Association will make an announcement on Tuesday about its investigation into Los Angeles Clippers owner Donald Sterling while fallout over racist comments allegedly made by him was building.
Sterling is being investigated by the NBA over racist comments he allegedly made that have since sparked widespread outrage in the United States.
The NBA - facing mounting pressure to take tough action against Sterling - said on Monday that Commissioner Adam Silver will address the media on Tuesday at a 2 p.m. ET (1800 GMT) news conference in New York City.
The NBA's announcement came shortly after some of the team's sponsors began pulling their financial support of the Clippers while Sterling's own family distanced themselves from him.
Auto dealer CarMax, a nine-year sponsor of the Clippers, was the first to announce it was ending its association, and was quickly followed by airline Virgin America and insurance provider State Farm.
"CarMax finds the statements attributed to the Clippers' owner completely unacceptable. These views directly conflict with CarMax's culture of respect for all," CarMax said in a statement."
State Farm said it is "pausing" its relationship with the Clippers while closely monitoring the situation.
"The remarks attributed to the Clippers' owner are offensive," State Farm said in a statement. "While those involved sort out the facts, we will be taking a pause in our relationship with the organization."
Silver said on Sunday that the NBA will "move extraordinary quickly in our investigation" after an audio recording surfaced over the weekend of a racist rant allegedly made by Sterling.
The Clippers owner, who made his fortune in real estate, has not issued any public statements but the alleged comments, which include telling a woman not to bring African-Americans to Clippers games, have drawn widespread criticism.
President Barack Obama weighed in, as did the Clippers players in a silent protest before Sunday's playoff game against the Golden State Warriors, while many Americans were calling for the NBA to send a clear message that such views will not be tolerated.
"This is a binding moment in the history of the NBA," said Sacramento Mayor and former NBA player Kevin Johnson, who is assisting the players union. "They (the players) are just outraged."
'FAMILY IS DEVASTATED'
If the NBA investigation confirms that Sterling did make the comments, he could expect a harsh punishment. There have already been calls for the billionaire to be removed as an NBA owner but he could also face a lengthy suspension and fine.
Such punishment is not unprecedented in North American professional sport.
Marge Schott, the former president and majority owner of Major League Baseball's Cincinnati Reds, was suspended for two years for slurs against African-Americans and Jews.
Schott eventually sold her controlling interest in the team.
Sterling's estranged wife Shelly released a statement on Monday condemning the comments attributed to her husband.
"Our family is devastated by the racist comments made by my estranged husband. My children and I do not share these despicable views or prejudices," she said.
"We will not let one man's small mindedness poison the spirit of the fans and accomplishments of the team in the city we love. We are doing everything in our power to stand by and support our Clippers team."
The Clippers are due to host the Golden State Warriors on Tuesday in the fifth game of their best-of-seven first-round playoff series.
The teams are currently tied at 2-2 but the series has been overshadowed by the race row. The fallout has even impacted the pre-game entertainment for Tuesday's game.
R&B recording artist Tank, who was scheduled to perform the U.S. national anthem, has withdrawn in protest.
"As an African American man and artist, I must take a stand on a matter that is so deeply personal to me," he told celebrity news site TMZ.com. (Reporting by Julian Linden in New York and Steve Keating in Toronto; Editing by Frank Pingue)