Stratford Westfield shoppers were evacuated after reports of a fire.
The alarm sounded after the east London shopping center had been empty for a few hours.
Social media videos show that people gather around the entrance to follow security orders.
Following reports of a fire at the first floor, around 40 firefighters and 8 engines rushed to the same shopping mall.
Photographs of the scene showed smoke coming out of a Watches of Switzerland store. Customers raced to leave the centre near the Olympic Park as smoke filled its main concourse.
More details are available.