An engineer says routine check-ups and reports of uneven road surface from the public could help reduce the incidence of road subsidence in the SAR.

Aaron Bok, former president of the Hong Kong Institution of Engineers, was speaking after traffic authorities partially reopened a stretch of road in Sham Shui Po last night after an eight by 12 metre hole opened up on Friday.

A section of Hai Tan Street was cordoned off after part of the carriageway plunged into a four-metre-deep hole that measured about eight by 12 metres.

Late on Sunday evening, the fast lane of Hai Tan Street, between Yen Chow Street and Kweilin Street, was reopened following temporary repairs.

Bok, who previously worked for the Water Supplies Department, warned that the SAR had thousands of kilometres of pipes that needed to be checked.

He said such incidents tended to be caused by construction activity or deep excavation or by damage to underground pipes.

He said the Sham Shui Po incident was probably caused by damage to nearby piping, and said regular surveys are needed.

Bok proposed that remote cameras could be used every two or three years.

"If during the survey they find there are some cracks or damage in the pipes, seal these holes immediately. That can prevent these small cavities from increasing," Bok said.

The government said permanent repair works would be carried out on the slow lane, which is expected to reopen to traffic before Wednesday’s rush hour.

Officials would then begin permanent repairs for the fast lane that would be completed on June 7.