The Detroit Lions violated player work rules set by the collective bargaining agreement during one of their practices this spring.

“On Friday evening the organization was made aware by the NFL and NFLPA that Organized Team Activities [OTA] practices held the week of May 27 violated player work rules pertaining to on-field physical contact pursuant to the Collective Bargaining Agreement,” the Lions stated. “As a result, the team’s OTA practice scheduled for Monday, June 10 has been forfeited.

“We take very seriously the rules set forth within the NFL’s Offseason Program and have worked to conduct our practices accordingly. We will continue to be vigilant with our practices moving forward.”

Per the collective bargaining agreement, practices held in phase three of the offseason program—the sixth, seventh, eighth and ninth weeks of the offseason—can’t include drills with live contact.