New York (CNN) -- Anthony Galea, a Canadian doctor who specializes in treating athletes, pleaded guilty Wednesday to a felony charge of introducing misbranded drugs into interstate commerce for the purpose of treating professional athletes, U.S. Immigration and Customs Enforcement said.
Those drugs included human growth hormone and Actovegin, a derivative of calf's blood, the ICE statement said. HGH is not approved by the Food and Drug Administration as a treatment for sports injuries and is banned by most professional sports leagues. Actovegin is not approved for any use in humans.
Galea admitted traveling to the United States "numerous times" from 2007 through September 2009 to treat professional athletes, including players in the National Football League and Major League Baseball, according to court documents.
Galea is not licensed to practice medicine in the United States.
Galea, 51, of Toronto, entered his plea before New York Western District Court Judge Richard J. Arcara in Buffalo, New York.
FBI Buffalo spokeswoman Maureen Dempsey was present for the court proceedings. Dempsey said that despite the prosecution's hesitance to release the names of any athletes that had received treatments, the prosecutor divulged three names at Judge Arcara's insistence.
The prosecutor named golf professional Tiger Woods, and two NFL players -- Takeo Spikes of the San Francisco 49ers and Jamal Lewis, formerly of the Cleveland Browns, according to Dempsey. Efforts by CNN to reach Wood, Spikes and Lewis, or their representatives were not successful Wednesday night.
According to Dempsey, the prosecutor confirmed the athletes got treatments from Galea, but did not all receive the same treatments. He did not say which treatments each received, but did say the players did not commit a crime by receiving the treatments as long as they never lied to investigators.
Dempsey said that Galea is believed to have treated over 20 patient/athletes, and the baseball and football leagues are anxious to find out what he will say when he meets with FBI investigators. Galea's plea deal requires he provide a statement on who he treated and how, as well as cooperate in any further investigations that may arise as a result.
"Here, the defendant admitted to not only bringing unapproved substances into the country repeatedly, but that he also practiced medicine without a license, supervised criminal conduct of others and obstructed justice through the actions of one of the defendant's Canadian employees. This case should therefore serve as a warning to all that such conduct will be prosecuted," said U.S. Attorney William J. Hochul Jr., for Western District of New York.
Galea faces a maximum three years in prison in addition to fines and forfeitures of up to more than $275,000 said Dempsey.
According to court documents, sentencing is set for October 19.
CNN's Susan Candiotti contributed to this story