Story highlights

Friday break-in reported at northern Georgia water treatment plant

Fluoride, chlorine levels were tampered with, leaving 400 unable to drink water

No harmful release of water, according to FBI; no sign of forced entry, manager says

Atlanta CNN  — 

Law enforcement agencies are trying to find out who tampered with chemical settings at a water treatment plant in northern Georgia.

About 400 customers were unable to drink the water Tuesday as authorities continued their investigation into the increased chlorine and reduced fluoride levels at the Carters Lake Water Treatment Plant, said Steve Smith, general manager of the Chatsworth Water Works Commission.

The FBI said there have been no harmful releases of water in Murray County since Friday’s break-in.

Pipes leaving the facility remained closed. They are expected to reopen later this week.

A plant employee Saturday noticed the adjustment in the levels, according to Smith.

There were no signs of forced entry at the plant, which had no video surveillance, Smith told CNN. Locks have since been changed.

The perpetrator appeared to be knowledgeable about the operation, officials said.

The FBI was called to assist state and local authorities, said Atlanta special agent Stephen Emmett.

“It is our understanding, however, that there were no harmful releases resulting from this tampering of settings,” Emmett said. “While there were no threats associated with this break-in, the FBI was called in out of an abundance of caution.”