Development Secretary Bernadette Linn on Wednesday reminded building owners that they don't have to wait for intervention by the authorities before carrying out checks to see if their properties are structurally sound, after yet another incident involving chunks of concrete falling onto the streets of Mong Kok.

There have been several such incidents in recent weeks, with some buildings affected more than once, and with injuries in some cases.

On Tuesday, a block of concrete smashed through the roof of a bus on Nathan Road.

"I want to remind owners that they don't need to wait for a building inspection notice to check on their property's condition," Linn said.

"Whether it is inside or outside, if there is injury from concrete falling due to a lack of maintenance, owners may have to bear criminal liability."

The government said last month that it would provide help to the owners of around 900 buildings who had ignored mandatory inspection notices.

A former chairman of the Hong Kong Institution of Engineers' building division, Adam Choy, told RTHK that the city has around 5,000 dilapidated private buildings in urgent need of repair.