The ASDA store in Bawtry Road, Doncaster, was evacuated yesterday afternoon after the fire alarms went off.
Shoppers were told to leave the premises before Doncaster fire crews arrived and found there was a small amount of smoke in the back office but no fire.
The incident was reported at 4.25pm and the premises were closed for around an hour.
Firefighters were also called to the Pony Paddock travellers’ site in Hall Villa Lane, Toll Bar, last night after an empty caravan went up in flames.
A spokesman said they managed to prevent the flames spreading to other caravans and the cause is still under investigation.