The NFL is working with platform providers and law enforcement to investigate a widespread hack of league- and team-connected social media accounts.

"On Monday, the NFL cybersecurity department became aware of a breach of a league-related social media account," the league said 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 Chicago Bears were the first Twitter account to be backed. One of the messages said the hack was to announce that "we're back" as well as to "show people that everything is hackable."