NFL teams were allowed to agree to contracts with undrafted players immediately, a source said Monday night.
Originally, the league announced that teams could not negotiate with rookie free agents until 10 a.m. ET on Tuesday. However, a change was made during the day and teams were notified they could start talking to undrafted players starting at 6 p.m. ET on Monday, the source said.
NFL spokesman Greg Aiello confirmed on Twitter on Monday night that teams were allowed to negotiate with all rookies starting at 6 p.m. Monday.
"Teams can negotiate with rookies tonight but not sign them until tomorrow," Aiello wrote.
According to sources, numerous undrafted players have already agreed to deals with NFL teams.
As the league enters a post-lockout world, the league has initiated so-called "transition rules" to govern the league as it resumes business activities.
As part of the transition rules, club facilities will open to players starting at that 10 a.m. Tuesday starting point, when teams' 2011 draft picks can be signed.
Also at 10 a.m. on Tuesday, teams can begin making trades and having conversations with veteran free agents from all teams. However, no player can officially sign until Friday at 6 p.m. ET. Teams will not have a window to negotiate exclusively with their own free agents.
However, when veteran free agents do sign with teams, they will not be able to participate in any practice, weight training or workouts until the beginning of the league year, scheduled to be Aug. 4. They will be required to attend classroom sessions and non-physical activities once the contracts are signed.
Rookies, both drafted and undrafted, will be allowed to fully participate and their contracts will be fully covered, regardless of whether Monday's agreement between players and owners is ratified.
Teams can begin reporting to training camps as early as Wednesday, depending on the date of each team's first preseason game.
John Clayton is a senior NFL writer for ESPN.com. Information from The Associated Press contributed to this report.