A Pittsburgh Steelers and others wait to leave the Federal Mediation and Conciliation Service building during extended NFL negotiations between owners and players on March 7.
NFL owners have locked out the players, signaling the start of the league's first work stoppage since 1987.
Union president and former player Kevin Mawae confirmed the lockout to The Associated Press in a text message early Saturday morning.
"We are locked out," he said. "We were informed today that players are no longer welcome at team facilities."
The league imposed the lockout hours after the union decertified. The decertification came after NFL owners and players broke off labor negotiations after they were unable to decide how to divvy up $9 billion a year.
The NFL had not released a statement as of 11:50 p.m. local time, nearly one hour after the deadline for a new collective bargaining agreement passed.
Other media reports said that team owners were locking out players.
Pro Football Talk reported that the NFL Network, which is owned by the league, confirmed the lockout on air.
The players also requested an injunction to block the lockout -- even before the league imposed it.
The Associated Press contributed to this report.