A huge blaze at an industrial unit that caused canisters to explode was started by overheated machinery, a fire service investigation found.
About 50 firefighters tackled the blaze, on the former airfield site at Parham in Suffolk, after explosions were heard on Thursday.
The fire, understood to be at a vehicle components factory, broke out at about 09:45 BST.
No-one was injured and crews remained in place on Friday.
A witness reported hearing "loud bangs and explosions", and plumes of black smoke could be seen for miles around the village, near Framlingham.
Richard Lapage, who was driving "a couple of hundred metres away" on Thursday morning, said the fire was "at Hatcher Components - a fibreglass place".
Suffolk Fire and Rescue Service sent 13 crews to tackle the "hazardous materials" fire and said the reported explosions were caused by empty chemical drums blowing up in the intense heat.
An investigation into the cause of the blaze, which destroyed the single-storey building, concluded the fire was "caused by machinery which had overheated".
A spokesman said one crew was still at the scene and a drone was checking for hotspots.
- 13 August