Of the 12 footballs that were allotted to the Patriots in Sunday night's 45-7 AFC Championship Game New England victory, 11 were determined to be under-inflated by 2 pounds of air (pounds per square inch), according to sources close to the NFL's investigation in an ESPN report late Tuesday night.
Footballs used in NFL games are required to be between 12.5 and 13.5 pounds per square inch.
The referee is the one judge of whether or not the balls used in play are adequate during a game.
The ESPN report did not say how the balls became under-inflated Sunday night. Earlier Tuesday, the league said it would wrap up its investigation into the matter in "two-to-three days."
It has been speculated that the Patriots could lose draft picks for using under-inflated footballs.
New England will play Seattle in the Super Bowl on Feb. 1 in Glendale, Arizona.