Residents living in Block 639 Ang Mo Kio Avenue 6 recently had to put up with a stench emanating from its void deck.
It drove one of them to share photos of a pipe spilling faecal matter onto the ground, and sewage water flowing into a nearby drain.
Signs of trouble first surfaced on Sept 3 when a resident contacted Ang Mo Kio Town Council, saying that the water in his toilet was unable to flow down his gully trap.
Although the issue was rectified on the day itself, the town council learnt of "an overflowing of faecal matter at the void deck" the next day, a spokesman told CNA.
The affected area was soon cordoned off and cleaned up.
While preliminary checks found a choked underground pipe, the town council said it is still investigating the exact cause of the pipe choke.
Waste matter has been temporarily diverted into the manhole in order to prevent further recurrence, the spokesman added.
The town council, together with the Home Improvement Programme (HIP) contractor, will continue inspection and rectification works today (Sept 7).
The HDB block, built in 1979, is currently under HIP, which helps resolve common maintenance problems of ageing flats such as spalling concrete.
ALSO READ: Couple's sewage disaster in new Punggol BTO flat explodes online