(CNN)A hacker gained access into the water treatment system of Oldsmar, Florida, on Friday and tried to increase the levels of sodium hydroxide -- commonly referred to as lye -- in the city's water, officials said, putting thousands at risk of being poisoned.

The incident took place Friday when an operator noticed the intrusion and watched the hacker access the system remotely. The hacker adjusted the level of sodium hydroxide to more than 100 times its normal levels, according to Pinellas County Sheriff Bob Gualtieri.

The operator immediately reduced the level back. At no time was there a significant adverse effect to the city's water supply, and the public was never in danger, Gualtieri said. It is unknown if the breach happened from someone locally, nationally or even outside of the United States.