Water utility Aqua Illinois is warning residents in University Park, as well as Green Garden and Monee townships, not to drink the tap water after elevated lead levels were discovered during testing.

In a statement, the utility said they are moving swiftly to identify the cause of the elevated levels, but do not believe it is related to infrastructure.

The advisory warned some residents not to drink, cook or use their tap water for brushing teeth, but to use bottled water instead. They also offered residents in the area free water-testing kits.

On Saturday, Aqua Illinois customers woke up to bottled water deliveries on their front steps as the company prepared to flush the entire water system.

Residents were told to expect to see technicians opening fire hydrants and that water discoloration from their faucets through Sunday was normal. Residents were told to run water through all fixtures for two minutes or until discoloration clears up, the company said.

Customers will receive updates through WaterSmart Alerts, the company’s automatic notification system, as they become available.