They claim it was dry u drains and a crack in the vent pipe in Block E... Note the "gov.hk". It wouldn't surprise me if the exact details were changed to save face.
A short documentary on Chinese Ethics:
The city is Shenzhen, which is a wealthy city like Hong Kong. Hell, this could also be a fomite of transmission for so many diseases. (The cooking of shit should kill the virus, but there is likely cross contamination between cooked and uncooked shit). Maybe the virus was spread in bat soup after all...