A toxicologist says the Northern Territory Government must extend its testing for arsenic at Mount Bundy station to the entire food chain, not just to water and land.
Last month, 17-year-old Ben Witham from the station died of suspected arsenic poisoning.
Eight more people, including the dead teen's parents and sisters, have recorded high levels of the chemical in their systems but are not ill.
Mount Bundy is a cattle station and popular tourist destination, about 140 kilometres south of Darwin.
More than 100 people were evacuated from the station at the weekend.
The Territory chief medical officer says there are very low levels of arsenic in Mount Bundy's drinking water but it is not dangerous.
He says the Government is now extending its tests to soil in an attempt to find the source.
University of South Australia Professor Ravi Naidu says it will be difficult to find the exact cause.
He says he would extend the tests to the foods that people at Mount Bundy have been eating, including the source of the food.
"The amount of that type of food that they eat, you know fish, and the volume of water that they drink," he said.
"If we did that, then we would be able to estimate the total daily intake of arsenic by the people who have been exposed to arsenic."
A 2008 report found that most of 96 water bores tested around the Darwin region contained arsenic.
Professor Naidu says, given the report, testing should be widespread.
"I would actually support the recommendation that this work should be extended to other regions," he said.
He says the report's recommendation for improved and more regular testing should also be followed.
Yesterday the Territory Government said the very low levels of arsenic in Mount Bundy's water is unlikely to impact on human health, even over a long period of time.
But Professor Naidu questioned the claim that the very low level of arsenic in drinking water is unlikely to have affected people's health.
He says his experience in Bangladesh is that people are harmed even if arsenic levels fall within half of drinking water standards guidelines.
"What we have seen with arsenic (levels) nearly half the drinking water guidelines... has led to significant poisoning of people in Bangladesh," he said.
"This was exposure for a duration of 10 to 15 years."
A public meeting on the Territory arsenic scare will be held tonight at the town of Adelaide River.