A hacker infiltrates the water treatment system of Oldsmar, Florida, and increases the concentration of caustic soda 100 times in an attempt to poison thousands of people.

The incident happened on February 5, when an operator of a water plant detected the intrusion and watched hackers enter the clean water treatment system remotely.

The operator immediately reduced the sodium hydroxide concentration to normal.

"Someone did something bad on purpose. It was a very bad deed, a very bad person," Gualtieri said on February 8.

However, the police chief said water from the treatment area will take 24-36 hours to reach the city's water supply system of more than 13,000 people and there will be a warning if the chemical concentration in the water is too high.

The Pinellas County Sheriff's Office, Federal Bureau of Investigation (FBI) and the Secret Service are investigating the intrusion.

Sodium hydroxide is the main ingredient in cleaning solutions.

The long-term effects of sodium hydroxide poisoning depend on the rate of dilution or neutralization of the poison in the system.

It is not clear whether an increase in sodium hydroxide in Oldsmar's clean water system will lead to any of these symptoms.