72-story tower in China remains closed after unexplained shaking

May 21 (UPI) -- One of the tallest buildings in southern China that shook earlier this week without explanation has been closed indefinitely for safety checks, officials said Friday.

The owner of the 71-story SEG Plaza in Shenzhen told all tenants and merchants to stay out of the tower starting Friday.

A document sent out by Shenzhen Electronics Group said the measure is intended to ensure that inspection work can be conducted "smoothly without any external disturbances."

The Shenzhen government wrote online that the main structure was safe and that the specific shaking was under investigation, but noted that the building would remain closed.

The wobbling lasted for a few minutes on Tuesday while 15,000 people were inside the building. The tower was evacuated and everyone made it out safely.

Officials have had a difficult time finding the cause. Earthquakes and structural damage have been ruled out.

The 20-year-old building is in the heart of Huaqiangbei, the world's largest bazaar of hardware and electronic components. The skyscraper, the 18th tallest structure in Shenzhen, was built in 2000 and houses a major electronics market and other business offices. Shenzhen has a population of about 13 million.

Poor construction standards in the country have been a concern for years. A hotel and a restaurant collapsed in China last year. Beijing officials have prohibited building skyscrapers taller than 1,640 feet.