A seven-storey building in Zunyi city, Southwest China's Guizhou province, collapse at midnight, June 10, 2015. [Photo/chinanews.com]

On Monday morning, the partial collapse of a residential building, built two decades ago, led to four deaths in the city of Zunyi in Southwest China's Guizhou province. It is the second incident of its kind in the city and the fifth nationwide within a month; a total of 22 people were killed in these collapses.

It is no exaggeration to describe these as disasters from the blue. Those who lost their lives will never know the true cause of their homes' collapse. But for those who survived the incidents and are now homeless, a thorough investigation needs to tell them what caused their homes to disappear without warning.

Residents who are aware of quality problems of their buildings need to be convinced about the safety of such buildings, which means related departments should conduct thorough quality checks of the overall condition of the buildings and make sure any problems identified are addressed.

Corruption used to be rampant in real estate development. It was not uncommon for realty developers to bribe officials to get land and all the necessary documents for their buildings to be built and enter the market.

These real estate developers would deduct such bribes from the funds earmarked for construction, which undoubtedly compromised the quality of the buildings they constructed. In addition, some realty developers intentionally spent less money than they should have on the construction of residential or other buildings in order to make more money and somehow managed to have their buildings pass the quality examinations by supervisors.

Early in the last decade when China's real estate sector was booming, there were a lot of complaints about the quality of residential buildings. The one that collapsed in Guiyang, capital of Southwest China's Guizhou province, on May 21, was built in 2003.

A thorough investigation is not just necessary to find out why these buildings collapsed and make sure those who are responsible are held accountable. It is also necessary to organize an overall nationwide check of all the buildings whose residents have lodged complaints. If serious quality problems are found, realty developers need to be made to pay compensation to homebuyers and rectify any safety issues.

Only in this way can the residential buildings in danger be prevented from falling down.