Office workers were evacuated on Wednesday lunchtime following concerns a blaze may have broken out.
The fire alarm at Breckland Business Centre in Dereham began blaring at around 12pm, forcing workers to retreat outside and into the adjacent car park.
One crew from Norfolk Fire and Rescue Service was sent to the scene.
It arrived at around 12.09pm, before firefighters delved inside the building to investigate the cause.
However, a spokesman for the fire service said the incident had been classed as a "false alarm".
Workers were able to return to their desks at around 12.50pm, with the fire crew leaving a few minutes later.
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