New England Patriots wide receiver Julian Edelman (11) cannot make the catch on a pass from Tom Brady during the first half of the NFL football AFC Championship game against the Indianapolis Colts last Sunday. - AP

THE National Football League (NFL) says its investigation into whether the New England Patriots used under-inflated footballs in the AFC Championship game is ongoing after a report late Tuesday claimed the league found 11 balls were not properly inflated.

Troy Vincent, the NFL executive vice-president for football operations, told The Associated Press the "investigation is under way and we're still awaiting findings."

Vincent was responding to an ESPN report that cited anonymous league sources saying 11 of the Patriots' 12 allotted game footballs were under-inflated by two pounds per square inch of air.

Vincent said earlier Tuesday he expected the probe to be concluded by the end of the week.

The last thing the NFL wants after a difficult season off the field is a potential cheating scandal that disrupts Super Bowl week. New England face the Seattle Seahawks on February 1, in Glendale, Arizona.

The Patriots, who beat the Indianapolis Colts 45-7 for the AFC title, said they were cooperating with the league, and a Seahawks spokesman said the team would defer to the league on the matter.