Lindsay H. Jones

USA TODAY Sports

DENVER — Officials correctly penalized the Denver Broncos for an illegal chop block on the play that injured Arizona Cardinals defensive end Calais Campbell, an NFL spokesman said Monday morning.

League spokesman Michael Signora told USA TODAY Sports via e-mail that the play was flagged because Broncos tight end Julius Thomas blocked Campbell in the "area of the thigh or lower" while left tackle Ryan Clady was engaging Campbell's upper body.

Signora said the Broncos also committed a "lure block" on the play because while Thomas went low, Clady, "confronts the defensive player in a pass-blocking posture but is not physically engaged with the defensive player."

The penalty on the play wiped out a 77-yard touchdown reception for Denver's Demaryius Thomas.

Campbell suffered what the Cardinals believe to be a sprained medial collateral ligament and is expected to miss about four weeks, head coach Bruce Arians said Sunday night.

Arians was livid about the block, calling it the "dirtiest play I've ever seen" and said that someone would need to "answer to that."

Signora said a decision whether Thomas or Clady, or both, will be fined will come later this week.

Thomas told USA TODAY Sports on Sunday night that he did not intend to hurt Campbell, and he sought out a Cardinals player to apologize to Campbell after the game. Thomas said there was a miscommunication with Clady that resulted in both players attempting to block Campbell simultaneously.

"I guarantee that being dirty is not a part of my game, and to intentionally hurt somebody is not something I would ever do," Thomas said.

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Follow Lindsay H. Jones on Twitter @bylindsayhjones