Federal investigators are investigating a report that hackers managed to remotely shut down a utility’s water pump in central Illinois last week, in what could be the first known foreign cyber attack on a U.S. industrial system.

The November 8 incident was described in a one-page report from the Illinois Statewide Terrorism and Intelligence Center, according to Joe Weiss, a prominent expert on protecting infrastructure from cyber attacks.

The attackers obtained access to the network of a water utility in a rural community west of the state capital Springfield with credentials stolen from a company that makes software used to control industrial systems, according to the account obtained by Weiss. It did not explain the motive of the attackers.

He said that the same group may have attacked other industrial targets or be planning strikes using credentials stolen from the same software maker.

The U.S. Department of Homeland Security and the Federal Bureau of Investigation are examining the matter, said DHS spokesman Peter Boogaard.

At this time there is no credible corroborated data that indicates a risk to critical infrastructure entities or a threat to public safety,” he said, declining to elaborate further. An FBI spokesman in Illinois did not return phone calls seeking comment.