According to a National Football League letter about the investigation into the controversy that was shared with the Globe, the Patriots were informed that the league's initial findings indicated that the game balls did not meet specifications. The league inspected each of the Patriots' 12 game balls twice at halftime, using different pressure gauges, and found footballs that were not properly inflated.

The next question is how did it happen?

According to ESPN, 11 of the 12 game balls were found to be underinflated by about 2 pounds each. The NFL specifications say they must be inflated to 12½ to 13½ pounds.


The investigation is still ongoing.

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A league spokesman declined to comment Tuesday, and earlier in the day, NFL executive vice president Troy Vincent told Pro Football Talk that the investigation would ideally be complete within two or three days.

If the Patriots are found to have deliberately doctored footballs, the organization can be fined a minimum of $25,000, and if the NFL finds the incident egregious, the Patriots could potentially lose a draft pick. In 2007, commissioner Roger Goodell took away a first-round draft pick and fined Patriots coach Bill Belichick after determining the team had spied on an opponent.

The Patriots defeated the Colts, 45-7, on Sunday night to earn their eighth Super Bowl appearance in franchise history. The next day, the NFL confirmed it was investigating whether the team used underinflated footballs.

The Colts reportedly grew suspicious after linebacker D'Qwell Jackson intercepted Tom Brady late in the second quarter. A softer football is easier to throw and catch, especially in rainy conditions, as was the case Sunday night.

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According to Newsday, Jackson gave the ball to a member of the Colts' equipment staff, who notified coach Chuck Pagano, who then relayed a message to general manager Ryan Grigson in the press box. He contacted Mike Kensil, NFL director of football operations, who then told the on-field officials at halftime.

On the first play from scrimmage after the opening kickoff of the third quarter, the officials held up the game for a minute and ultimately switched out the game ball. Former NFL official Mike Carey, working the broadcast booth for CBS, surmised that "It looks like they still spotted the ball for a kicking ball, waiting for one of the ball guys to come down and give them a regular ball."

The investigation will attempt to find out if the Patriots tampered with the footballs after the referee inspection. It's possible that cold temperatures affected the pressure of the footballs, but it was an unusually warm 51 degrees at kickoff.

At least one official touches the football on every play, yet none seemed to notice until halftime. The Patriots led, 17-7, at intermission, and outscored the Colts, 28-0, after the officials seemingly corrected the ball issue.

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Per the NFL rulebook, each team provides game officials with 12 footballs before the game, and the balls are required to be inflated between 12½ and 13½ pounds per square inch. The referee inspects the game balls 2 hours and 15 minutes before kickoff, places a special marking on each ball that passes inspection, and hands the approved balls to attendants on each team, who are supposed to maintain custody of the balls on each sideline.


Each team uses its own football on offense — a 2013 New York Times article said that each team even has its own logo on the football when on offense — and teams are allowed to slightly doctor the footballs to their preference. "Rubbing up" the football with dirt to make it less slippery is common, and so is slightly adjusting the inflation levels.

Packers quarterback Aaron Rodgers likes to overinflate the football. When the Packers and Patriots played on Nov. 30, CBS broadcaster Phil Simms relayed a conversation he had with Rodgers.

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"He said something which was unique. 'I like to push the limit to how much air we can put in the football, even go over what they allow you to do, and see if the officials take the air out of it,'" Simms said of Rodgers. "Because he thinks it's easy for him to grip. He likes them tight."

Rodgers defended the practice Tuesday on his radio show on ESPN Milwaukee.

"It's not an advantage when you have a football that's inflated more than average air pressure. We're not kicking these footballs," he said.

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It's unclear how often the NFL investigates ball issues. In another incident this season, the NFL reminded all 32 teams that they cannot warm the balls with sideline heaters during cold games, after the Panthers and Vikings did it in their Nov. 30 game in Minneapolis, drawing a warning from officials.

"If something is noticed, it's not unheard of for a ball to be removed from circulation and then tested during the week for whatever issue there was," head of officiating Dean Blandino said.

Ben Volin can be reached at ben.volin@globe.com. Follow him on Twitter @BenVolin