NEW YORK -- The NFL suspended linebacker D.J. Williams, defensive tackle Ryan McBean and tight end Virgil Green of the Denver Broncos for violating the league's policy on performance-enhancing substances.

The league announced the suspensions on Friday.

McBean and Williams are suspended for Denver's first six games of the 2012 season. Green is suspended for the team's first four games. All three are suspended without pay.

Williams and McBean were found to allegedly have "non-human" urine in their system, a source told ESPN senior NFL writer John Clayton.

The players are eligible to participate in all offseason and preseason practices and games.

The situation is similar to what Ryan Braun of the Milwaukee Brewers went through this past winter. The person who administered the test was relieved of his duties as a collector for allegedly violating protocol required for testing, a source told Clayton.

Williams and McBean are considering a lawsuit against the NFL and are challenging some of the procedures in the hearing, a source told Clayton.

Williams issued a written statement calling his suspension unjust and vowing legal action. Green tweeted that he has now been approved for the medication for which he has been suspended.

Williams said in his written statement that the NFL contends the urine sample he provided to an NFL specimen collector for testing wasn't from a human.

"We proved -- conclusively -- at the NFL hearing on this matter that the NFL and its specimen collector wholly failed in their duties to safeguard and process my specimen properly," Williams said. "In fact, the specimen collector was fired by the NFL after compromising my specimen as well as others'. The hearing officer, an NFL executive, ignored the NFL's own policy, engaged in inappropriate communications with top NFL officials about this matter without my knowledge or approval, corrupted the system, ignored that my specimen had been compromised, and now has subjected me to humiliation as well as suspension."

Williams' lawyer Peter R. Ginsberg said the specimen collector, whose name he wouldn't disclose, has said he watched Williams void directly into the specimen bottle, so it would've been impossible for the specimen to be non-human.