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NEW YORK (Reuters) - A Canadian sports doctor was charged on Tuesday with unlawfully treating three National Football League players with unapproved drugs, including human growth hormone (HGH), U.S. authorities said.

Dr. Anthony Galea, who has treated golfer Tiger Woods, was named in a criminal complaint filed in Buffalo, the U.S. Attorney's Office for the Western District of New York said in a statement.

Galea is charged with lying to federal officials, smuggling, unlawful distribution of HGH, introducing the unapproved drug actovegin into interstate commerce and conspiracy to defraud the United States, the complaint said.

The smuggling charge carries a maximum prison term of 20 years, it said.

The Toronto doctor was charged in December by police in Canada with selling an unapproved drug and smuggling.

The football players allegedly treated by Galea were not named and the NFL said it had not been informed of their identities.

"We have been in touch with law enforcement and will continue to cooperate with the federal authorities as the case moves forward," NFL spokesman Greg Aiello told Reuters.

"We obviously have a very strong interest in learning who these players are and about their involvement with any prohibited substances so that we can enforce our policies."

The complaint said one of the players received injections of actovegin from Galea and a second allegedly had two kits of HGH delivered to his residence at Galea's direction. A third player was allegedly treated numerous times in the United States by Galea.

An affidavit supporting the complaint alleges Galea, who is not an American citizen and not authorized to work in the United States, repeatedly entered the country from 2007 to September 2009 to treat numerous professional athletes.

The athletes were said to be from Major League Baseball, the NFL and the Professional Golfers' Association.

Major League Baseball said it was monitoring the case.

Woods has denied ever taking illegal drugs and said in April he received treatments for injuries from Galea.

Galea's Canadian lawyer Brian Greenspan said in a statement his client looked forward to the opportunity to respond to the allegations at the appropriate time.

"It is regrettable that Dr. Galea, a world renowned and respected sports medicine physician, now faces these further charges," said Greenspan. "However, as this matter is now before the court, it is not proper to comment further."

(Writing by Gene Cherry in Raleigh, North Carolina; Editing by Frank Pingue and John O'Callaghan)