ATLANTA -- A Delta Air Lines flight that left Atlanta bound for Chicago was ordered to turn around by the Transporation Security Administration and return to Hartsfield-Jackson International Airport Thursday.

A Delta representative told CBS Atlanta News that the flight was ordered to come back for an "additional security sweep."

A spokesperson for the Department of Homeland Security said passengers on a previous flight noticed other passengers acting suspiciously. Because of that, the spokesperson said, the TSA ordered the plane to come back for the additional security sweep.

After passengers exited the aircraft, the plane was swept by a K-9 team and cleared to depart. The flight departed at 6:57 p.m. The report of suspicious behavior was investigated and found to be unsubstantiated, the statement said.