The NFL sent a memo warning teams not to release contract terms before free agency officially opens Tuesday, reports "The memo makes clear that we will look into any potential violations of the rules," league spokesman Greg Aiello told the website.

The league issued the warning after reports surfaced with details on new contracts for Ndamukong Suh, Jeremy Maclin, Byron Maxwell and Frank Gore, the report said. A three-day negotiating window opened Saturday, but players cannot sign until 4 p.m. ET Tuesday.

"At this time, the league office is beginning investigations into a number of reported agreements with clubs. Violations will be dealt with accordingly," the letter stated.