Police, fire and ambulance crews were called to the Groundwell Industrial Estate in Swindon town in England around 7.30pm.
Wiltshire Police said it was working to evacuate the immediate area, but said there was no need for other nearby residents to evacuate.
The force urged people who live nearby to stay inside, close all windows and avoid the area of the industrial estate for their own safety.
At least 10 fire engines and specialist vehicles, including an aerial ladder platform and water carriers, are on the scene, according to Dorset and Wiltshire Fire and Rescue Service.
It said its firefighters were dealing with a large warehouse fire and were working to get the fire under control.
Several local residents posted online to say they had felt the explosion.
Chloe Hackett wrote on social media that there was a "massive explosion" and her house "literally shook".
She said: "Huge fireball. Really hope there is no one hurt and hope the emergency services keep safe from harm."
Angela Willis said: "I wondered what that huge noise was. Shook my doors. I thought someone was trying to break in. I hope all ok for those involved and hoping nobody got hurt."
MNA/
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