Darren Hayman, the acting director of Gold Coast Water, stated that no clue can be found out about how E. coli got into the drinking water supply at Nerang.

Reports say that over the weekend, about 2,500 households had to boil their drinking water.

Hayman said that the investigation is on to find out the possible cause of contamination despite the requirement that was lifted yesterday.

He says the water quality tests that raised the original alarm may be suspect and inspections have cleared pipes and reservoirs in the area.

He added, "It requires a very stringent controlled environment to collect that test - in a sterile environment - and it's possible that sometimes those tests can be corrupted. The tests we have taken since Friday have definitely indicated a clear result."

GCW chair, Daphne McDonald, added that to figure out the source more tests would be done in the next week.

He added, "The alert has now been lifted and residents in the affected areas can return to drinking the town water supplies without needing to boil the water first."