Josina Anderson talks about the NFL investigating the Giants' use of walkie-talkies during their game against the Cowboys. (2:18)

Questions need to be answered on Giants' walkie-talkies use (2:18)

The NFL is investigating the New York Giants' use of a handheld, two-way radio in the fourth quarter of Sunday night's 10-7 victory over the Dallas Cowboys, a source told ESPN's Todd Archer, confirming a report by the New York Post.

Coach Ben McAdoo was seen using a walkie-talkie to relay plays to quarterback Eli Manning when the Giants were having problems with their headsets early in the fourth quarter. Coaches are not allowed to hold any two-way radios during a game.

Another source told ESPN the Cowboys have not filed a formal complaint with the league, but that the NFL had already begun its own investigation of the Giants' use of handheld, two-way radios.

Stephen Jones, the Cowboys' chief operating officer and executive vice president/director of player personnel, wouldn't confirm Thursday that his team has contacted the NFL.

"We don't comment on things like that," he said, referring to whether they called the NFL, "but it's obvious to everybody what happened, and my understanding is it's being looked into and handled."

Jones said the team believes the use of the walkie-talkies did not play a part in the outcome of the game.

The rule is in place because walkie-talkies provide nonstop access to the quarterback's headset and cannot be cut off by the league's "cutoff switch operator." League rules state that communication between the quarterback and the sideline must be cut off when 15 seconds remain on the play clock.

A backup quarterback is allowed to hold a two-way radio, but he's not permitted to speak into it.

The Giants declined to comment Thursday.

Wide receiver Odell Beckham Jr. and Manning were seen running to the sideline to get the plays on a drive in the fourth Sunday night against the Cowboys. The Giants did not score on the drive.

"I just wasn't getting anything, so I had to run to the sideline to get the plays,'' Manning told the Post. "Four plays maybe, we don't have signals for stuff. It happened to be all run plays. If it's pass plays, [backup quarterback Ryan] Nassib or somebody could signal them to me. I had to run to the sideline, sometimes he was giving it to Odell [Beckham Jr.] right there, and Odell would run to me and get the play in. Like high school.''

It wasn't long before McAdoo resumed communication with Manning.

"I don't know when he was on the walkie-talkie or not,'' Manning said. "I just knew it was back in my ear, and we were going.''

McAdoo is in his first year as an NFL head coach. He spent two seasons as the Giants' offensive coordinator after eight seasons as an assistant with the Green Bay Packers.

ESPN's Todd Archer and Josina Anderson contributed to this report.