The farm at the heart of a salmonella outbreak that sparked a nationwide lettuce recall could learn the cause of the contamination in coming days.

Tripod Farmers recalled 30 of its retail products sold at supermarkets, as well as wholesale products distributed to hospitals, schools and businesses last week after numerous cases of people becoming sick after consuming it.

Investigations are underway to determine whether a contaminated water supply, fertiliser or something else at the Bacchus Marsh facility is to blame and results are expected this week.

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Tripod Farmers managing director Frank Ruffo said the company was focused on the health and safety of consumers, establishing the cause of the problem, and fixing it.

“In the interests of public safety, we have recalled the entire production batches from which the positive samples were detected,” he said.

Tripod Farmers has suspended some of its farming and processing operations while the investigation is being carried out and until the problem has been fully identified and fixed.

But the company has been given the go-ahead by authorities to resume business after a site inspection and “superwash” of the facility last week.

On Saturday afternoon, authorities increased the number of salmonella cases in Victoria from 54 to 62, but food histories have not yet been conducted on the new patients.

This means the eight new cases are not confirmed as lettuce-related.

Other states and territories are examining up to 30 possible cases of salmonella infection but whether the cases are linked to the outbreak strain in Victoria is still yet to be confirmed.

A Health Department spokesman said investigations are continuing, but it could take some weeks before the cause of the outbreak is determined.

Anyone who has bought any of the affected lettuce mixes with a best-before date leading up to February 14 should return them to the store, or throw them out.