Tripod Farmers recalled 30 of its loose-leaf salad mixes from supermarket shelves last Thursday after Victoria's Health Department traced a number of salmonella cases to its products.

Since then, 62 cases of salmonella have been confirmed in Victoria and a further 30 around the country are being investigated.

The cause of the contamination is expected to be identified when test results become available in the coming days.

In a statement, Tripod Farmers said further test results were expected "early this week". However, health authorities have said it could be "weeks" before the source is confirmed. 

Coles and Woolworths have cancelled their salad mix orders from Tripod Farmers, which employs 400 people, until the source of the problem is identified.

As a result, the company has suspended some of its operations despite being given the green light by health authorities to resume harvesting and packing following an inspection and so-called "superwash" last week.

The outbreak has also affected sales of Australian salad mixes in Thailand.

A spokesman for the Thai Ministry of Public Health, Suwannachai Wattanayingcharoen, has advised Thai consumers who purchased the Australian-sourced salads to dispose of them or return them to the point of sale.

The warning came after the ministry was notified by the United Nations' International Food Safety Authorities Network (Infosan) over the salmonella outbreak.

Trade officials are reportedly concerned about the impact of the warning on Australia's exports to Asia. Department of Foreign Affairs and Trade figures show that in 2014-15, Australia exported $48.3 million in fruits and nuts to Thailand, and $A43.9 million in "edible products and preparations".

Tripod Farmers - a family business based in Bacchus Marsh - was established in 1989 and grows 809 hectares of lettuce in Melbourne, Gippsland and the Sunraysia regions.

The recalled lettuce includes brands such as Coles 4 Leaf Mix, Woolworths salad mix, SupaSalad Supamix and Wash N Toss salad mix. They have best-before dates leading up to and including February 14.

Managing director Frank Ruffo said on Saturday that the company was continuing to work with health authorities.

"The company apologises to everyone affected by the recall, and thanks the public for the way it is responding to the recall," Mr Ruffo said in a statement.

Symptoms of salmonellosis usually occur between 6 to 72 hours after the bacteria is ingested, according to the Health Department.

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.