Eleven of the 12 balls used by the New England Patriots in their AFC championship win over the Indianapolis Colts were under-inflated, according to a report.
The NFL announced that it was investigating the matter after Colts linebacker D'Qwell Jackson brought a ball he had intercepted from Tom Brady to the sideline and instructed to his coaches that he felt it was under-inflated.
After conducting an investigation into the matter the league has reportedly discovered that 11 of the 12 balls used by the Patriots were two pounds below the PSI level required by the NFL's regulations, reports ESPN.
The NFL's senior vice-president of communications Greg Aiello said: "We are not commenting at this time."
Patriots spokesman Stacey James added: "We have been in complete cooperation with the league and will continue to do so."
New England could face a punishment of a $25,000 (£16,543) fine or the docking of Draft picks if found guilty of tampering with the balls before the match.
