One of China‘s tallest skyscrapers has been evacuated after it mysteriously started to shake, sending panicked shoppers running to safety.
The 980ft SEG Plaza started swaying at 1pm on Tuesday in the southern city of Shenzhen, causing a mass exit from the building.
No earthquakes have been recorded and authorities remain baffled as to what caused the motion.
The 79-storey building was sealed shut as of 2:40pm, according to local media reports.
Completed in 2000, the tower is home to a major electronics market as well as various offices in the downtown of one of China’s fastest-growing cities.
Emergency management officials are investigating what caused the tower in Shenzhen’s Futian district to wobble, according to a post on the Twitter-like Weibo platform.
One theory shared by Lu Jianxin, a chief engineer at China Construction Science and Industry Corp, posits that the rare phenomenon was caused by mechanical resonance, which occurs when a structure’s natural oscillations time up with an external force.
He told the Shenzhen Special Zone Daily: ‘If there was no earthquake today, it would be unusual for SEG Plaza to have such a situation.
‘Judging from the currently available information, this could be an accidental frequency coincidence, that is, resonance.’
The local weather report showed a wind speed of 27mph at the time which should not have caused such an issue for the building.
‘After checking and analysing the data of various earthquake monitoring stations across the city, there was no earthquake in Shenzhen today,’ the statement said.
‘The cause of the shaking is being verified by various departments.’
It was not immediately clear how authorities will handle a dangerous building of its scale in the heart of a city of over 12 million people.
Bystander videos published by local media on Weibo showed the skyscraper shaking on its foundations as hundreds of terrified pedestrians ran away outside.
‘SEG has been completely evacuated,’ wrote one Weibo user in a caption to a video of hundreds of people milling about on a wide shopping street near the tower.
Ji Jialin, who was on the 14th floor at the time of the swaying today, said the evacuation happened on her lunch break.
She told the South China Morning Post: ‘The shaking didn’t seem strong from the 14th floor… we all escaped with others by taking the stairs.’
Traffic resumed near the building by 6pm but it remained roped off.
It is not yet known when it will open.