An SA Health investigation has found raw eggs were likely the source of a salmonella outbreak linked to an Adelaide bakery chain.

A salmonella outbreak that hospitalised 19 people was likely caused by the handling of raw egg products at an Adelaide bakery chain.

Director of Public Health Services Fay Jenkins said SA Health collected samples from three Angkor Bakery stores last week, after 51 cases were linked to the outbreak.

"Given the sample results and the strain of the salmonella outbreak, it is most likely that the cause of contamination was related to handling raw egg products," Dr Jenkins said on Thursday.

"The external shell of eggs may contain harmful bacteria such as Salmonella, and while eggs may not necessarily look or smell 'off' they may be contaminated."

Following the outbreak, SA Health said the cases involved people who ate Vietnamese rolls from the bakery.

All three outlets closed during the investigation, but two have since returned negative Salmonella testing results and reopened.

A store at Salisbury Downs remains closed while SA Health continues to work with management.

Dr Jenkins said raw egg ingredients can be risky if they are not appropriately handled, and could contaminate foods including aioli, mayonnaise, hollandaise, tartar sauce and mousse.

"It's important to check that eggs are clean and not cracked or dirty - and those that are should be thrown out," she said.

"Preparation surfaces and utensils should be thoroughly washed, sanitised and dried after handling eggs."

Salmonella symptoms include fever, diarrhoea, vomiting, headaches, stomach cramps and loss of appetite.

More severe symptoms may occur in young children, older people, pregnant women and people who have compromised immune systems.