Minneapolis, MN -- (Sports Network) - NFL security interviewed a number of Minnesota Vikings officials on Tuesday regarding tampering charges levied by the Green Bay Packers over Brett Favre.

The Minneapolis Star Tribune, citing people with knowledge of the situation, reported that the NFL's security department visited the Vikings' facility in Eden Prairie, Minnesota.

The Packers filed the tampering charge against Minnesota last week, claiming "inappropriate dialogue" between the Vikings and Favre, who retired this offseason as the Packers quarterback but now wants to play again.

The Milwaukee Journal Sentinel reported Tuesday that Favre continued to use a Green Bay-issued cell phone after his retirement, and that phone records show repeated calls to Vikings coach Brad Childress and offensive coordinator Darrell Bevell.

If the Vikings are found guilty of tampering the team could be fined or face the forfeiture of draft picks.