Hackers successfully infiltrated the computer system controlling a water treatment facility in the city of Oldsmar, Florida, according to a report from the Tampa Bay Times

The hackers remotely gained access to a software program, named TeamViewer, on the computer of an employee at the facility to gain control of other systems, sheriff Bob Gualtieri said in an interview with Reuters.

“At no time was there a significant adverse effect on the water being treated,” Pinellas County Sheriff Bob Gualtieri said during a press conference on Monday, which was later posted to YouTube. “Importantly, the public was never in danger.” Sodium hydroxide, commonly known as lye, is used in water to regulate acidity levels, the Tampa Bay Times reports, but in excess it can be dangerous to human beings because it’s the same inorganic compound used in corrosive household cleaners like Drano.

The intruder spent between three to five minutes inside the system and changed the the sodium hydroxide level from 100 parts per million to 11,100 parts per million.

The change was immediately reverted by the operator and the population of Oldsmar was not at risk at any moment because the operator intervened immediately. The plant operator then cut off remote access to the system.

Eric Seidel, the mayor of the city, said that Oldsmar water treatment system is set up with redundancies that would have sounded an alarm if the water’s chemical levels reached dangerous levels.

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