A further 1400 homes and businesses have been added to a contamination testing zone near former industrial sites in Adelaide's suburbs.

The Environment Protection Authority (EPA) told residents of Clovelly Park and Mitchell Park on Thursday that it needs to conduct more tests to determine the extent of groundwater and soil vapour contamination from trichloroethylene (TCE), used as a metal cleaner in industrial settings.

The tests are expected to begin next month and take up to four months to complete.

EPA operations director Peter Dolan says there are no immediate health risks but residents have been told not to use bore water for any purpose until further notice.

“We have indicated all along that our priority is the people in the area and undertaking the further investigation work as soon as possible,” he said in a statement.

Residents in 31 homes in Clovelly Park this month learnt they will be relocated after elevated levels of TCE were found in their soil and air.

TCE can be carcinogenic when people are exposed to high levels over an extended period.

The opposition has called for environment minister Ian Hunter to resign or be sacked after it emerged that the government had known about elevated contamination levels at Clovelly Park for about six weeks before raising the issue with residents.

Opposition leader Steven Marshall says EPA tests revealed in 2009 that Mitchell Park was at risk from drifting chemical vapours but no further tests were conducted in the suburb.

“Heads must roll,” he told reporters on Thursday.

“The government has known about this issue since 2009. They’ve kept it hidden from the people in the adjacent areas and only because of the Liberal Party and the media working together to expose the issue is anything happening.”

Mr Hunter has consistently defended his handling of the issue, saying the government has been proactive in communicating with residents about contamination from old industrial chemicals.