The water systems were hacked earlier this week.
Federal and state authorities are investigating whether Iran or hackers associated with the country were behind a series of coordinated cyberattacks at more than 30 water plants in Minnesota earlier this week, according to multiple U.S. officials.
The officials told ABC News they are also waiting for a more detailed level of forensics from the hack.
They stressed that the analysis is preliminary, and another official says that the U.S. has not made any formal announcement or determinations on who might be behind the cyberattacks.
The probe into the Iranian connections was first reported Thursday by the New York Times.
Minnesota IT Services (MNIT) did not disclose details about the attacks that took place on Sunday and Monday, but the state agency said there were no requests from cities for their residents to change their drinking water usage.
"The investigation remains active, and responders continue to assess affected systems. The Minnesota Department of Health continues to work directly with affected water systems to help ensure public health remains protected," MNIT said in a statement Tuesday.
The hacks in Minnesota mirror a similar pattern carried out in other states by suspected Iran-linked actors.
The FBI said in a statement that the agency is aware of the intrusions but did not assign responsibility.
The acting director of the Cybersecurity and Infrastructure Security Agency (CISA) urged state and local governments to sure up their systems to protect against these kinds of attacks.
"CISA is aware of multiple potential incidents affecting local water utilities and is coordinating with the EPA and other government and industry partners to understand the scope and provide any information or technical support to help critical infrastructure owners and operators protect their systems," acting director Nick Andersen said in a statement.
-ABC News' Ivan Pereira contributed to this report.
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