A recall affecting pre-packaged lettuce amid fears of a salmonella outbreak has grown much wider than first thought.

A salmonella outbreak affecting pre-packaged lettuce sold at Coles and Woolworths has spread wider than first thought.

Victoria's Department of Health and Human Services has received reports of 28 cases of salmonella anatum strain linked to pre-packed lettuce distributed by Victorian-based company Tripod Farmers.

Anyone who has purchased any of the affected lettuce mix with a best-before date leading up to February 14 should return it to the store or throw it out.

"We've been assured that there's no risk associated with the products after that date," senior medical adviser Dr Finn Romanes said on Thursday.

Originally the outbreak was said to affect only the pre-packaged lettuce sold at supermarkets, but Lite n' Easy customers are also warned the lettuce recall will affect some lunches in its menu this week.

It has dumped the lettuce supplier following the recall.

Sandwiches sold at 7-Eleven have also been recalled.

There are unconfirmed reports the affected lettuce has also been used in souvlaki and burgers made at a Victorian school canteen.

TriPod Farmers managing director Frank Ruffo said the company was working closely with health authorities.

"We are shocked at the test results because we put public safety first and foremost and comply with all Australian health and safety standards," Mr Ruffo said in a statement.

AusVeg acting CEO Jessica Lye won't comment on reports the outbreak is linked to manure because an investigation is under way.

There have been no reported cases of salmonella linked to the pre-packaged lettuce in NSW, according to the state's health department.

RECALLED PRODUCTS (Use-by date up to and including February 14)
* Woolworths Baby Spinach 100g
* Woolworths Baby Rocket 100g
* Woolworths Gourmet Mix 100g
* Woolworths Fresh Cut Loose Baby Spinach 1kg
* Woolworths Fresh Cut Salad Loose Mesculin 1kg
* Wash N Toss Watercress 100g
* Wash N Toss Sorrel 50g
* Wash N Toss Baby Cos 100g
* Wash N Toss Baby Spinach 100g
* Wash N Toss Salad Mix 100g
* Wash N Toss Wild Rocket 100g
* Wash N Toss Kale 100g
* Coles Australian Baby Spinach 60g
* Coles Australian Baby Rocket 60g
* Coles Australian Baby Rocket 120g
* Coles Australian Spinach & Rocket 120g
* Coles Australian Baby Spinach 120g
* Coles Australian 4 Leaf Salad 120g
* Coles Australian 4 Leaf Salad 200g
* Supa Salad Supa salad 180g
* Supa Salad Green Coral 180g
* Supa Salad Supamix 1kg
* Supa Salad Spinach 1kg
* Supa Salad Rocket 1kg
* Supa Salad Baby Cos 1kg
* Supa Salad ALH 1kg
* Supa Salad Spinach 180g
* Clear Film Blend
* Clear Film Spinach
* Clear Film Baby Cos