It was excavation works for the Downtown Line 2 that caused last Saturday's massive sinkhole on Woodlands Road. The construction destabilised the soil, which ruptured an underground water pipe.
The soil movement and pipe's rupture then weakened the ground under the road, causing the sinkhole to open up.
That is according to the Land Transport Authority (LTA), which has concluded its investigation into the cause of the incident.
The sinkhole, which was as wide as one of the road's lanes, appeared near West View Primary School, next to where construction work for Downtown Line 2 is being carried out.
It is the second one that has been reported near a construction site for the new train line, which will run from Bugis to Bukit Panjang. The first happened last July, when a section of Bukit Timah Road near the Newton flyover, in the direction of the Stevens Road intersection, sank.