Authorities say the FBI, Georgia Bureau of Investigation and a sheriff's department are investigating a break-in at a water treatment plant in the north Georgia mountains.

About 400 water customers around the small community of Ramhurst have been ordered not to drink water following the Friday break-in at the Carters Lake Water Treatment Plant in Murray County.

Chatsworth Water Works manager Steve Smith said the FBI began investigating because a water plant break-in could potentially fall under the realm of homeland security.

Smith said someone changed the settings for how chlorine and fluoride feed into the system. Smith said the water company's tests show none of the changed levels of chemicals ever made it out of the plant, which was shut down as a precaution.

Tags: FBI, Georgia Bureau of Investigation, water treatment plant, Murray County, FBI investigation, ramhurst