But a Federal Health Department spokesperson said its investigation into the outbreak, which now affects 34 people in five states and the ACT, "is ongoing". At least two samples show traces.

"The source of the hepatitis A virus is still unconfirmed. However, the berries are the only common exposure for all cases," she said.

"Specimens from 27 cases of the outbreak have been genotyped and found to have an identical genetic sequence. This indicates that all the cases contracted the hepatitis A virus from a common source."

Patties Foods, which began recalling frozen berry products sourced from Chile and China from February 13, has ruled out "systemic failure", saying overseas microbiological and viral testing found no links between the fruit and the disease.

The testing was only on Nanna's one-kilogram mixed berries, as it was the only product of four recalled epidemiologically linked to the health crisis.

"Extensive microbiological and viral testing conducted by Patties Foods shows no evidence of systemic failure of Patties Foods' quality assurance programs," said Patties Foods chief executive Steven Chaur.

The Health Department, according to Patties, tested samples from two opened packs recovered from customers who fell ill. One sample tested positive for hepatitis A. But health officials said the pack could have been contaminated after being opened.

The department also tested eight packs purchased randomly from supermarkets in Victoria. Seven tested negative. One sample had a trace amount.

"DHHS noted that the detection of HAV, under the testing protocol, only demonstrated the virus was or is present. It did not allow for a determination of whether the virus is viable, that is, whether the virus is alive and will cause infection."

Patties, based in Melbourne, recalled Nanna's one-kilogram bags of frozen mixed berries and frozen raspberries, and Creative Gourmet 300- and 500-gram bags of mixed berries.

They remain off supermarket shelves. Patties is looking for alternative suppliers.

Mr Chaur remains cautious. He said its global investigations were coming to a close.

"If our Nanna's product was the source, the lack of laboratory findings from the testing conducted by Patties Foods for the presence of E. coli, coliforms or HAV indicates there has been no systemic failure," he said.

"Regardless, Patties Foods has significantly increased protection measures to ensure that any risk is further minimised in future."

He said after health fears were raised, Patties recalled all potential source product, ceased importing from possible sources of the potential contamination, and increased our testing regime to 100 per cent containers of its imported frozen berries from all countries, not just China.

Patties has also tightened E. coli testing to its "most sensitive".

"Patties Foods has also re-tested as a precautionary measure all batches of frozen berries not subject to the recall in our Australian warehouses. This includes berries and fruits from Chile, Vietnam and Peru. No evidence of HAV or E. coli has been detected in any batch," Mr Chaur said.

Patties sent about 360 packs of frozen berries to laboratories Australia, Europe and North America for Hepatitis A testing.

Fifteen people in Queensland, 11 in NSW, four in Victoria, two in Western Australia, one in the Australian Capital Territory and one in South Australia are believed to have contracted hepatitis A after eating the suspect berries.

Chances of further cases are low as the 50-day incubation period has ended.