A spokesman for HDB said it was informed last month that the flat owner had died in the flat.

"Early this month, we received feedback about (the) smell, pests and pet issues at the unit. Efforts to locate the (man's) next-of kin were, however, unsuccessful," said the spokesman.

In view of the condition of the flat, HDB put forth a final appeal for the next-of-kin to clean the flat by Dec 16 but by that deadline, no one had come forward.

On Thursday, HDB and Bishan-Toa Payoh Town Council cleaned up the unit.

"We first combed through the flat and confirmed that there were no more cats in the unit, and then proceeded to clear the insects and rubbish, as well as wash the flat," said the spokesman.

The cleaning is still in progress and is expected to be completed by today.