The news broke late Tuesday night.
According to ESPN, the balls used in Sunday's championship game were under-inflated by two pounds per square inch.
Before each game, the ball is inflated to an air pressure of 12.5 to 13.5 pounds per square inch. The balls had been inspected two hours before kickoff by referees.
The NFL spent the day in Foxborough conducting numerous interviews. They reportedly have gathered most of their information. The ESPN report cites NFL sources, though the league did not comment Tuesday night.
The Patriots say they will continue to cooperate in the investigation.
The team could face fines of up to $25,000 or loss of draft picks if the balls were found to be deflated.
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