Hackers destroyed a pump used by a US water utility after gaining unauthorized access to the industrial control system it used to operate its machinery, a computer security expert said.

Joe Weiss, a managing partner for Applied Control Solutions, said the breach was most likely performed after the attackers hacked into the maker of the supervisory control and data acquisition software used by the utility and stole user names and passwords belonging to the manufacturer’s customers. The unknown attackers used IP addresses that originated in Russia.

Weiss cited an official government report from the state where the regional water district was located. It was dated November 10, two days after the hack was discovered. The document indicates that the utility had been experiencing unexplained problems with its computerized system in the weeks leading up to the breach.