US homeland security and FBI officials are investigating an apparent cyber-attack on a water utility near Springfield, Illinois.
The attack may have been the cause of a water pump shutdown, and could be the first case of foreign hackers successfully targeting a US industrial facility.
The shutdown did not result in any supply issues, but the incident triggered a high-level investigation.
On 8 November a technician said the system has been hacked from a computer in Russia. The incident was made public by a cybersecurity expert, Joe Weiss. "This is a big deal," he told the Washington Post.
US press reported that the company's database was compromised with hackers retrieving the supervisory control and data acquisition (Scada) software. During the attack the Scada system was turned on and off, burning out the water pump.
Homeland security spokesman Peter Boogaard told news agencies that officials had yet to confirm the incident was the result of a cyber-attack."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.
Scada systems control infrastructure such as water treatment facilities, gas pipelines, railway switches, chemicals plants and nuclear reactors, making them prime targets for attack.
Their vulnerability came to light last year after centrifuges at a uranium enrichment facility in Iran were attacked by Stuxnet, a virus which targets Scada systems.
According to US nuclear experts Stuxnet increased the speed of uranium centrifuges to breaking point while shutting off safety monitoring systems.
Last year Iran's president, Mahmoud Ahmadinejad, confirmed the virus had "managed to create problems for a limited number of our centrifuges".
In 2007, researchers at the US government's Idaho National Laboratories identified a vulnerability in the electricity grid, demonstrating how much damage a cyber-attack could inflict on a large diesel generator.