The sinkhole on Woodlands was reported to be as wide as one lane and appeared next to ongoing construction work for Downtown Line 2 - making it the second sinkhole to appear near a Downtown Line 2 construction site.

By 7:30am yesterday, the affected stretch near West View Primary School was reopened for traffic, including normal operations for thirteen bus services, that were initially re-routed due to the road closures. An SMRT spokesman told The Straits Times that its passengers were informed about the temporary diversion through posters at bus stops while staff also conducted patrols in affected areas to provide assistance to passengers.

Last Saturday's cave-in is the fourth reported this year - after two along Clementi Road and one along Keppel Road. Land Transport Authority (LTA) is still investigating the cause of the earlier sinkholes. According to Geotechnical engineers, underground water pipe leakages and excavation are two possible causes for the sinkholes.

Mr Chong Kee Sen, Vice-President of the Institution of Engineers Singapore, explained, the geological make-up of a mixture of soft soil and hard rock poses a challenge, as Singapore continues to dig underground to build rail lines and lay pipes. He also mentioned boring through soft soil weakens and moves the soil, which might cause the road to weaken and sink when it is heavily used.

He suggested a tighter maintenance regime for underground pipes and to closely monitor the movement of soil during tunnelling works.