NEW YORK — Internal affairs detectives are investigating claims by former tennis professional James Blake that he was thrown to the ground and then handcuffed while mistakenly being arrested Wednesday at a hotel, police said. Blake, who's biracial, used to train at Saddlebrook Resort, a tennis academy in Wesley Chapel. He told the Daily News he wasn't sure if he was arrested because of his race but said the officer who put him in handcuffs inappropriately used force."To me it's as simple as unnecessary police force, no matter what my race is," he told the newspaper. "In my mind there's probably a race factor involved, but no matter what, there's no reason for anybody to do that to anybody." One officer was placed on modified assignment after investigators reviewed surveillance footage, the New York Police Department said in a statement early Thursday. It said a probe of the incident was ongoing. A cooperating witness misidentified Blake to detectives investigating fraudulently purchased cellphones as one of two people he recognized as being involved with the scheme, NYPD spokesman Stephen Davis said. "Once Blake was properly identified and found to have no connection to the investigation, he was released from police custody immediately," Davis said in a statement. Police Commissioner Bill Bratton, speaking on the NY1 cable television news station, said Blake "has a right to be upset." Bratton vowed to aggressively address Blake's allegations. "It's very disturbing," Bratton said. "The nature of what he described is not what we do. It's not what we're supposed to do." Officers arrested a suspect in the cellphone scam at the Grand Hyatt New York hotel in Manhattan during a controlled buy earlier Wednesday, police said. It was after that buy that a deliveryman with the cellphone company pointed out Blake and another man in the hotel lobby as having purchased cellphones the day before, officers said. The second man, who Bratton said was standing next to Blake, was taken into custody. A hotel security guard, a former member of the NYPD, recognized Blake, prompting the arresting officers to confirm his identity. Bratton said internal affairs detectives were sent to the hotel and had already identified several witnesses. Blake's last tournament as a professional was the 2013 U.S. Open, at which he lost in the first round of singles and doubles. He was ranked as high as No. 4 in the world and reached three Grand Slam quarterfinals, including at the U.S. Open in 2005 and 2006. Blake, 35, was born in Yonkers and went to high school in Connecticut. He attended Harvard University before turning pro in 1999. He has owned property in the Tampa Bay area, including an Avila mansion he purchased in 2005 and later rented out. The mansion was set ablaze by one of those renters, Darrin Campbell, in May 2014, after Campbell shot his wife and two children in the head, then shot himself, according to law enforcement.