The New England Patriots said on Saturday they had followed "every rule to the letter" and accepted no blame for using footballs that were under inflated in their AFC championship win over the Indianapolis Colts six days ago.
The victory earned the Patriots a spot in the Feb. 1 Super Bowl against the Seattle Seahawks.
The National Football League is investigating why balls used by the Patriots against the Colts were under inflated.
"I believe now 100 percent that I have personally and we as an organization have absolutely followed every rule to the letter," Patriots head coach Bill Belichick told a news conference.
Belichick said he had spent a lot of time this week experimenting with the preparation of balls for games and had discovered that atmospheric conditions could affect ball pressure.
"When the footballs go out on to the field in the game conditions, whatever those conditions are... that's where the measurements would possibly be different than what they are in a controlled environment," the coach told reporters.
