Brighton's largest shopping centre was evacuated because of a fault in the sprinkler system.
Hundreds of shoppers and staff were forced to leave Churchill Square when a faulty sprinkler went off and triggered alarms.
Stores lost about two hours of trade because of the evacuation at 4pm on Saturday. Churchill Square was closed until 5.45pm after repairs were made to the sprinkler, checks carried out and the system restocked with water.
Staff were let back in before customers who had a few minutes to shop before the centre closed.
Centre manager Derek Maddison said the faulty sprinkler was in a staff stairwell above Borders Books.
He said: "The position of it was in the lobby at the top of a service and fire exit staircase.
"I have been in shopping centres for 20 years and this is only the second time I have seen a sprinkler go off for no apparent reason."
He said fire investigators believed the sprinkler may have had sunlight reflected on to it through a skylight.
A spokesman for Borders said there had been some minor damage to stock.
A launch party on Saturday evening to celebrate the bookshop securing a licence to sell alcohol had to be cancelled.
A spokesman for the fire service said: "The building was evacuated as a precaution."
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