(SportsNetwork.com) - Eleven of the 12 footballs allotted to the New England Patriots for Sunday's AFC Championship Game were under-inflated, according to a report.

Citing league sources close to the NFL's investigation, ESPN.com reported the 11 balls were each under-inflated by 2 pounds of air pressure.

NFL rules mandate game balls be inflated to 12 1/2 to 13 1/2 pounds per square inch (PSI).

"We are not commenting on the matter at this time," NFL spokesman Michael Signora told SportsNetwork.com in an email late Tuesday evening.

The NFL launched an investigation following New England's 45-7 win over the Indianapolis Colts in a rain-soaked game at Gillette Stadium, which advanced the Patriots to the Super Bowl against Seattle.

A deflated football is said to be easier to throw and catch in inclement weather.

If the Patriots are found to have deflated footballs intentionally, they could be subject to penalties, including a possible forfeiture of drafts picks.

A source told ESPN the league was "disappointed ... angry ... distraught" over the findings.

According to NFL rules, game balls are required to be inspected by the referee two hours and 15 minutes before kickoff and may not be altered after that.

A Patriots spokesman said the team continues to cooperate with the league's investigation.