Thomson Police Chief Joseph D. Nelson confirmed that one suspect fled the scene and was being sought.
Another officer said there were no injuries.
The Federal Bureau of Investigation and the Georgia Bureau of Investigation joined in the investigation.
Nelson said a more complete statement will be released Tuesday, by his office or by the GBI.
Thomson K-9 officer Sgt. Jamie Smith led Angus across a grassy area near the bank, but the dog was unable to pick up a trail. K-9 trackers from the Columbia County Sheriff's Office arrived for backup, but were not called into duty.
Investigators walked and drove through the adjacent residential neighborhood and thicket for about two hours after the robbery but did not disclose the object of their search.
Shopkeepers next door to the bank seemed surprised when asked about the commotion at the bank. The restaurant, a barber shop, real estate office, attorney's office and other businesses remained open.
Customers drove up to the bank, even crossing the yellow police tape, asking whether the bank was open. An elderly man carrying a Social Security envelope asked bystanders, who directed him to another SunTrust branch about a mile south on Main Street.