Higher than expected levels of a toxic industrial chemical have been detected around homes in Beverley in Adelaide's inner west, the Environment Protection Authority (EPA) says.

The EPA stepped up testing for trichloroethene (TCE) in the area west of Port Road in October after the Clovelly Park contamination scare.

Preliminary results on tests carried out in April and this month have revealed levels of TCE in groundwater are still too high.

The presence of the chemical in soil vapour was tested for the first time and found to be higher than expected.

Residents in the affected area have been notified and further tests will begin on Monday.

The EPA's director of science, assessment and planning Peter Dolan said the level of risk to the public was not yet known.

"[The results are] significant enough that we need to do some further work to find out whether people might be exposed to these chemicals," he said.

"We've got some more work to do about the nature of the houses - whether or not it can get into houses.

"The houses in this area appear to be 1950s vintage with crawl spaces. That tends to reduce the risk.

"We haven't confirmed what the likely exposure is for people."

Mr Dolan said some of the results were at a level that, if detected inside homes, would require steps to better ventilate those properties.

"If we find levels ultimately which are high enough we would need to take or recommend some remedial action," he said.

TCE was detected in groundwater in the area when it was first tested in 2007 and 2008, and the EPA has repeated its warning to residents not to use bore water.

It said contractors would be drilling small shallow bores in the area over the next few weeks as further testing is carried out, including in crawl spaces beneath homes.

"We don't believe we've found the edge [of the affected area] so we've got to check and see how contained this is," Mr Dolan said.

The EPA suspects the contamination is decades old and caused by previous industrial activity.

An interim report assessing the health risks of the contamination is expected to be ready in July, and a community group is being set up to keep residents informed.

The EPA said TCE is used in industry as a degreasing solvent.