Brighton's largest shopping centre was evacuated on Saturday after a fault in the sprinkler system.
The firefighters were despatched to Churchill Square at 4pm when a fire alarm sounded.
Hundreds of people were sent outside as a precaution after an apparent fault with a sprinkler system.
A Sussex Police spokeswoman said there was a water leak in a lift shaft which shorted the electrics. This set the alarms off.
She said the cause was thought to be a leak above Borders book shop.
A spokesman for the fire service said: "There was a fault with the sprinkler system and the building was evacuated as a precation.
"There was some minor damage."
Nobody from Borders was available for comment.
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