Sites around RAAF Base Tindal near Katherine in the Northern Territory have tested positive for toxic firefighting chemicals.

A dozen Australian military bases have been tested for the firefighting foams previously used by Defence, which contain contained per- and polyfluoroalkyl substances (PFAS).

Preliminary test results in the NT have been delayed, after they were due to be released in September.

Defence says its report on the initial testing will be released in November.

The department has been working collaboratively with experts from the Department of Health, which has advised that there is no known consistent evidence of health effects.

Early reports say there were two detections of contamination from nine samples taken at RAAF Base Tindal.

Four samples were taken at Robertson Barracks and three at RAAF Base Darwin, but it is unclear whether contamination was detected.

Defence has been supplying a single Katherine property with an alternate supply of drinking water, which each individual has to apply for.

There are plans in place for detailed testing to begin next year, which could take up to 12-months, and include an assessment of risks to human health and the environment.

Reports say the regime will also include testing fruit, and even sinking bores to test aquifers in Katherine.

The NT investigation is still at a very preliminary stage, but residents can apply for compensation including calling for Defence to purchase affected properties.