(CNN) -- At least one person was shot at a food-service container plant near Atlanta on Friday morning, and the shooter is believed still inside the plant, a federal source with knowledge of the situation said.
Gunfire was reported at Dart Container Corp. in Conyers, about 25 miles east of downtown Atlanta, and authorities are looking for a shooter, Rockdale County Sheriff's Deputy Lee Thomas said.
Thomas didn't specify whether anyone was injured.
The federal source who told CNN of one person shot spoke on condition of anonymity.
At least three schools and the county school transportation offices were placed on lockdown, Rockdale County schools said on Twitter at 8:34 a.m. ET.
"All of our students & staff are safe. No visitors are allowed on campus at this time," the tweet reads.
Police cars with lights flashing were parked outside the Dart Container facility.
Dart Container manufactures and distributes food-service products such as cups, plates, containers, lids and straws, at plants and centers across the country, including the Conyers plant, the company's website says.
People with the FBI's area field office are heading to the scene to support local agencies leading law enforcement's response, the federal source said.