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A "white hat" hacker group claimed responsibility Monday for hijacking the social media accounts of the NFL and several of its teams.

OurMine, a Saudi hacking account that promotes its own cybersecurity services, said it hacked a number of the league's accounts on its Twitter page. The first team to be exposed appeared to be the Chicago Bears, on Sunday.

"Apologies that our account was compromised this morning," the team tweeted Sunday.

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By Monday, the group appeared to have compromised the NFL's official Twitter account and social media accounts of several teams, including the Kansas City Chiefs, who will play in the Super Bowl on Sunday. NFL reporter Dov Kleiman began a Twitter thread of screenshots for accounts that appeared to be have been compromised, counting 15 teams that were hacked.

The San Francisco 49ers, the Chiefs' opponent in the Super Bowl, confirmed to NBC News that their Twitter account was also compromised.

"We are aware of the issue and are working with NFL cyber security and the platforms to address it," the 49ers said in a statement.

The NFL and the Chiefs did not immediately respond to requests for comment.

OurMine bills itself as a "white hat" hacking group, the term for cyber trespassers who breach systems with good intentions. It began taking responsibility for a number of hacks Monday, claiming the intention was to announce its return and to "show people that everything is hackable."

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Someone responded to questions from NBC News through an email account that appeared to belong to OurMine. The person said that OurMine stopped its work in 2017 "due to some issues" but that it was now back.

OurMine said it didn't publicly take responsibility for the 49ers hack because, while it accessed the account, the platform locked it before OurMine was able to tweet. It did not say how it was able to access the various NFL accounts.

"We pick our targets randomly, and we already tried to contact them before the tweets but we didn't receive any response yet," the group said.

OurMine also said it believes the Chiefs will win the Super Bowl.