Smoke from a faulty compressor led to Sainsbury's supermarket at North Walsham being evacuated this morning.
Shoppers at the store on Bacton Road abandoned their trolleys and joined staff in the car park outside after the alarm sounded at about 10.20am.
Firefighters from North Walsham, Mundesley, Aylsham and Sheringham rushed to the scene.
Peter Rowe, station manager at Sprowston, said the incident had been confined to a plant room, detached from the main store.
A crew, wearing breathing apparatus, had been sent in to investigate but no-one had been hurt, there had been no flames, no damage and firefighters had not needed to take further action.
Store manager Andy Stewardson said the fault had been with a compressor and shoppers had been able to return after 45 minutes to an hour later.
'We followed procedure and the evacuation was carried out very quickly,' he added.
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