Utility companies in at least seven states have reported cyberattacks on water and wastewater systems to the FBI. 

In some of those incidents, water systems had to be shut down, The Hill reported. 

Last month, 30 Minnesota towns and cities were hit by a "coordinated cyberattack." Michigan is now reporting cyberattacks on nine of its water systems. 

The FBI and the Environmental Protection Agency are warning that malicious cyber actors are targeting internet-connected equipment used by water and wastewater utilities, causing "operational disruptions" and raising concerns about the security of critical infrastructure.

The Cybersecurity and Infrastructure Security Agency (CISA) issued an advisory last week, warning that Iranian-affiliated hackers were attacking critical infrastructure, including water and wastewater systems. The advisory stresses the importance of "restricting direct internet access." It said that some of the larger attacks on water systems resulted in boil-water notices and "sustained manual operations." 

Speaking to reporters at Camp David on Friday, Trump denied Iran is behind the attacks and blamed Minnesota's leadership and Gov. Tim Walz.