AN explosion of an electrical switchboard sparked a fire at Kingaroy Shoppingworld's Big W last night.
Fire crews were called to Big W at 9.37pm yesterday, and Big W staff had to be evacuated and electricity was turned off.
Kingaroy Queensland Fire and Rescue Service Area Commander Mark Long said it took five hours to contain the blaze.
"We had 12 firefighters attend the fire and it took some time to clear the complex of gases and smoke," he said.
Commander Long said it was still unclear what caused the switchboard to explode and said investigations were continuing this morning.
The store is closed for the day.