(CNN)With less than a week to go until Super Bowl LIV, the NFL is dealing with a breach that saw the Twitter accounts for nearly half of the league's teams get hacked.
Among the teams affected by the breach, which took place over several hours Monday, were the San Francisco 49ers and Kansas City Chiefs, who are playing in the Super Bowl this weekend.
The NFL said Tuesday it had managed to secure all league and club accounts.
The NFL's official Twitter account appears to have been affected, along with the accounts of the Chiefs, 49ers, Green Bay Packers, Dallas Cowboys, Denver Broncos, Indianapolis Colts, Houston Texans, New York Giants, Philadelphia Eagles, Tampa Bay Buccaneers, Los Angeles Chargers, Cleveland Browns, Arizona Cardinals and Chicago Bears.
Dov Kleiman, an NFL reporter, posted screenshots of the accounts that appear to have been hacked.
Most of the accounts tweeted out this message along with contact information: "Hi, we're back (OurMine). We are here to show people that everything is hackable."
The hacker group OurMine took responsibility for the attack. OurMine previously targeted HBO, The New York Times and Twitter CEO Jack Dorsey, among other notable figures and organizations.
"On Monday, the NFL Cybersecurity department became aware of a breach of a league-related social media account," the NFL wrote in a statement. "Targeted breaches and additional failed attempts were discovered across the league and team accounts.
"The NFL took immediate action and directed the teams to secure their social media accounts and prevent further unauthorized access. Simultaneously, the league alerted the social media platform providers and, with their assistance, secured all league and club accounts. We continue to work diligently with the teams, which have resumed normal operations.
"The NFL and teams are cooperating with its social media platform providers and law enforcement."