Two teenagers were arrested inside the empty Northampton town centre BHS on Sunday after a 999 call reported a smell of burning coming from the shop.
Three fire engines were dispatched to Abington Street at around 10.40am yesterday (Sunday) after the emergency services were called.
Fire crews found two small fires inside the empty BHS store, which were brought under control and extinguished.
Two 16-year-old boys were arrested on suspicion of burglary. Eyewitnesses reported seeing the boys wearing goggles and rubber gloves as they led by police to the squad car.
The teenagers have been released under investigation in connection with the incident. An investigation into what happened is underway.