Shoppers have been evacuated from Debenhams at Westwood Cross.
One mum at the store said an emergency message was given out over the tannoy and the alarms were sounding.
She carried her young daughter down the emergency exit into the loading bay area with other customers who were on the first floor. Those on the ground floor use the main exit.
Staff and customers are now outside but do not yet know what caused the alarm.
UPDATE: The store is back open for business as usual now. Store bosses say it was “just a routine, practice evacuation.”