Cylinders containing propane gas caught fire at the side of a derelict house at Queen Street close to the junction of Henry Street shortly after 7pm.
Such cylinders have a built-in safety mechanism. A specially designed plastic valve on top of the cylinder melts in extreme heat allowing the gases inside to safely burn off.
However, once tipped over the cylinder can instead shoot missile-like over a distance of a couple of hundred feet.
Alternatively, the volatile gases can explode causing a fire ball.
The road was condoned off by police and a 200 metre exclusion zone put in place.
Up to 40 people were evacuated from near-by properties as a precaution.
Two fire appliances were at the scene to cool the tanks and the area was deemed safe approximately one hour later.
A spokesperson for the Northern Ireland Fire and Rescue Service, said:
"We received a call at 19.11hrs regarding two gas cylinders alight outside a derelict property.
"Two Fire Appliances from Ballymoney Fire Station attended. Firefighters used cooling jets to cool the cylinders and turned the gas supply off at the valve.
"As standard practice with a gas cylinder incident a 200m exclusion zone was put in place and nearby properties evacuated.
"PSNI were informed of the incident and the gas supplier was informed to remove the cylinders.
"Fire crews were finished at 20.30hrs."
Both the Fire Service and police said the cause of the fire was not yet known.