ABC News: Some events honoring military at pro sporting events were paid for by the Department of Defense, according to an audit revealed Wednesday. (5:29)

The NFL is auditing its teams' marketing contracts with the Department of Defense and has offered that teams return money if it finds that patriotic tributes were specifically paid for by the DOD.

The audit was revealed Wednesday in a report compiled by Arizona Sens. John McCain and Jeff Flake, who are investigating what has become known as "paid patriotism" events. The comprehensive report, which investigated 122 contracts that the Department of Defense had with sports organizations from 2012 to 2015, included a letter written by NFL commissioner Roger Goodell dated Nov. 2.

"If we find that inappropriate payments were made," Goodell wrote, "they will be refunded in full."

Money Paid to NFL Teams From DOD A look at the NFL teams that received the most money from the Department of Defense for patriotism tributes from 2012 to '15: Team Money 1. Falcons $879,000 2. Patriots $700,000 3. Bills $650,000 4. Ravens $534,500 5. Saints $472,875 6. Chargers $453,500 6. Seahawks $453,500 8. Colts $400,000 9. Vikings $375,000 10. Jets $327,500

It's unclear how far back the NFL's audits will go.

In July, the NFL issued guidance to each of its 32 clubs to make clear that "any on-field recognition, community events, or other activities that are not specifically in the form of recruitment or advertising should never be included in contracts or otherwise performed for payment."

At a news conference Wednesday, McCain requested that any money that teams return be funneled into veterans' causes.

Of the five major sports leagues (including MLS), the Department of Defense spent the most on contracts with NFL teams. The report discloses contracts with 19 teams, from 2012 to 2015, for a total of $6.1 million. The DOD spent $4.4 million on deals with the other four leagues combined.

The team that received the most from the DOD was the Atlanta Falcons, who had agreements worth $879,000 over the past four seasons. The team received payments for the color guard to step onto the field during the Falcons' military appreciation game, for the performance of the national anthem by a member of the Georgia Army National Guard and for 80 members of the guard to hold the American flag on the field.

Flake and McCain hope that President Obama will sign an amendment to the 2016 National Defense Authorization Act (NDAA) that would prohibit the DOD from paying for events such as flag ceremonies and honoring soldiers.

McCain and Flake said in Wednesday's report that the Department of Defense "cannot accurately account for how many contracts it has awarded or how much has been spent." Although the goal was for this to serve for recruiting purposes, the two senators said the department "doesn't uniformly measure how and whether the activities under contract are actually contributing to recruiting."