Researchers have tied the problem to widespread over-extraction of groundwater, particularly in lower-income neighbourhoods where piped water is scarce.

Initial tests had suggested the netting was up to standard, but investigators had not been able to check all of it earlier due to the fire.

There are currently three unfilled Cabinet posts, with one more expected on Tuesday after Investment, Trade and Industry Minister Tengku Zafrul Abdul Aziz ends his tenure as senator.