The NFL is investigating whether text messages were sent to the Cleveland Browns' sideline during games, league spokesman Michael Signora told ESPN.com on Friday.

Texting would be a violation of the NFL's rules prohibiting electronic communication during games.

Signora did not elaborate except to say the league is looking into the matter.

"We are reviewing internally and will fully cooperate with the NFL on this matter," the Browns said in a statement.

Though it's not clear who sent the messages and who received them, a team source said the messages were subject of discussion among some players and coaches late in the season.

Cleveland.com originally reported the text messages were sent and said it was one issue in former offensive coordinator Kyle Shanahan leaving the team. He perceived it as interference from the front office regarding coaching decisions.

According to a report, texts to the Browns' sideline contributed to offensive coordinator Kyle Shanahan's decision to leave the team. Ken Blaze/USA TODAY Sports

Though no texts have become public, the messages regarded personnel decisions and play calls, the source said.

The league's electronic devices rule states:

"This prohibition ... applies to the use of any electronic communication devices, including but not limited to a cell phone, smart phone, tablet device, or any type of computer, whether online or stand-alone, including laptop and hand-held computers, in the coaches' booths, on the sidelines, in the locker room (after kickoff), or in any other club-controlled area on game day beginning ninety (90) minutes prior to kickoff and continuing through the end of the game, including halftime (with the exception of League-issued tablets used for coaches' still photos).

"Team doctors and members of the athletic training staff are permitted to use tablet devices, cell phones, smart phones, or similar devices within the bench area and locker room to communicate player injury information, but may not communicate competitive or strategic information.

"Club football operations staff members are permitted to use cell phones outside the coaches' booths, bench areas, and locker rooms only when handling non-competitive and/or non-strategic communication."