Federal investigators confirmed to Sky News that they were examining reports that a foreign hacker or hackers managed to remotely gain access to a water facility in Illinois and shut down a pump on November 8.
The incident came to light after prominent cyber security expert Joe Weiss obtained a report written by the Illinois Statewide Terrorism and Intelligence Centre.
According to Mr Weiss, who specialises in protecting industrial control systems from electronic threats, the report confirms the cyber attack was traced back to a computer in Russia.
He told Sky News: "The report says 'An information technology services and computer repair company checked the computer logs of the system and determined the computer had been hacked into from an internet provider address located in Russia.'"
DHS spokesman Peter Boogaard said: "At this time there is no credible corroborated data that indicates a risk to critical infrastructure entities or a threat to public safety."
Mr Weiss, a control systems cyber security consultant and managing partner at Applied Control Solutions based in California, said he did not understand the equivocation from DHS, and that the report was definitive, even if it did not explain the attacker's motives.
He said: "The title of the report is Public Water District Cyber Intrusion. That's kind of hard to work around. Something happened."
The cyber attack reportedly targeted a water facility in a rural area west of the state capital, Springfield. Read More