Wollongong City Council confirmed it ordered testing after residents reported a ‘’putrid odour’’ emanating from the Parkes Street site. Results are expected in four weeks, the council said.

It appears the contamination is not the result of any recent incident or the current building works at the site.

Residents claim at least six people have been diagnosed with cancer - all living within a space of 16 houses.

Despite the multi-level government investigation, there is no evidence at this stage the cancers are the same type, linked, or caused by environmental factors.

Director of Public Health Illawarra Shoalhaven Curtis Gregory said the council had made contact.

‘’We are waiting on details around the assessment of the site and any information around contaminants,’’ Mr Gregory said.

‘’At this early stage of the investigation there is not a lot of details so it is too early to say anything about the health of residents, but it is something that we will be looking at.’’

In a letter to Helensburgh residents, the council said it had raised the concerns with the Environmental Protection Authority and NSW Health ‘’to determine how we proceed’’.

‘’Council staff met with local residents who had raised concerns about odours and potential contamination of the site,’ the March 3 letter said. ‘’Council is investigating and has issued a direction requiring the developer to undertake effective soil sampling,’’ the letter said.

‘’Council has also issued a notice requiring the developer to implement effective sediment and erosion controls. The council urges residents with questions about their health to contact their doctor in the first instance.’’

In a letter to Local Government Minister Gabrielle Upton, a resident said they believed a cancer cluster existed ‘’due to the fact we have had three deaths from cancer, one case of a terminal cancer resident, two others who have had tumours removed recently and one young woman who has had a brain cyst which is inoperable’’.

They said a ‘’putrid smell emanates from the site … causing headaches runny noses and coughs’’.

A council spokesman said a senior manager had met with residents concerned about ‘’a potential contamination’’.

‘’The residents advised council of a number of people diagnosed with cancer in the immediate vicinity,’’ the spokesman said. ‘’As a result council is now investigating the history of the site.’’

The Cancer Council warns it is important to differentiate between a "cancer cluster" and a normal pattern of cancer diagnoses.

A cluster feature an unusually high number of the same type of cancer occurring in a group of people with a common exposure.