NFL officials issued a memo Monday to warn its 32 teams not to reach contract agreements with unrestricted free agents before the league’s 2015 free agency window officially begins Tuesday, according to reports. The league made clear its intention to investigate potential violations after contract details involving several high-profile free agents were made public over the weekend.

League rules permit teams to extend “pitches” to prospective unrestricted free agents over a three-day period which began Saturday and ends Tuesday at 4 p.m. EDT, at which point teams are officially allowed to offer contracts. But these pitches can’t be construed as actual offers, nor can team representatives contact players directly. Moreover, teams and players are not allowed to agree to contract terms during the negotiation window, according to ESPN.

“You are reminded that the purpose of the three-day negotiating period is to create a level playing field in the competition for Unrestricted Free Agents, by permitting clubs to express interest in a prospective UFA and to exchange information with certified agents regarding the level of compensation envisioned by the club and the agents. Any attempt to undermine the purpose of this negotiating period may be considered conduct detrimental to the League,” the memo said, according to Pro Football Talk.

Despite these rules, several teams and players have purportedly reached final agreements on new contracts since Saturday. For example, the Miami Dolphins agreed to a deal with former Detroit Lions defensive tackle Ndamukong Suh worth approximately $114 million with $60 million guaranteed, according to ESPN’s Chris Mortensen. Similarly, league sources confirmed to ESPN that former Philadelphia Eagles wide receiver Jeremy Maclin has already agreed to join the Kansas City Chiefs for a contract worth $11 million per year.

Other NFL rules regarding the three-day negotiation window prevent teams from constructing a sample contract a prospective free agent and from scheduling trips for players to visit with staff when free agency officially begins. Pro Football Talk has a full roundup of the rules here.

“At this time, the league office is beginning investigations into a number of reported agreements with clubs. Violations will be dealt with accordingly,” the memo added.