Raw tomatoes are suspected of being linked with a salmonella outbreak in the United States. (Shari Vialpando/Associated Press)

Tomatoes grown in California and Florida are safe to eat, according to U.S. health officials investigating a salmonella outbreak that has sickened 167 people and prompted retailers and restaurants to stop selling certain raw tomatoes.

California and Florida are the largest tomato growing regions in the U.S.

The outbreak is also believed to have contributed to the death of a 67-year-old Texas man.

No illnesses have been reported in Canada. Canada's food watchdog says it will not issue a tomato recall until a definitive link between tomatoes and the outbreak has been demonstrated.

But a number of restaurants in Canada and the U.S., including Tim Hortons, McDonald's, Burger King, Taco Bell, KFC, Boston Pizza and Milestones have stopped serving raw tomatoes in their meals as a precautionary measure. All Colemans Food Centres stores in Newfoundland and Labrador have stopped selling foreign-grown tomatoes.

According to the U.S. Food and Drug Administration, the following types of tomatoes are not likely linked with the salmonella outbreak:

• Cherry tomatoes.
• Grape tomatoes.
• Tomatoes with the vine attached.
• Home-grown tomatoes.

The FDA investigation is focusing on raw red Roma, raw red plum and raw red round tomatoes.

Dr. Douglas Powell, head of the International Food Safety Network, said the FDA is now looking at Mexico as a possible source of tomatoes linked with the outbreak.

"Through a process of interviewing people some common themes have come out and so far they're able to determine — it's probably these Roma tomatoes or the big red ones but only from certain areas and right now it's looking like Mexico," Powell said.

Powell also noted that it is possible tomatoes possibly linked with the salmonella outbreak in the U.S. may have also been shipped to Canada.

"We import tomatoes from various regions — this outbreak goes back to April so I'm not exactly sure what product was being imported during those months, but it could be that some of the same product that was in the U.S. made its way up to Canada," he said.

Consumers should check tomatoes to see where they were grown before purchase, he said.

"Often the tomatoes have a sticker on them which may even say the growing region, like for instance it may even say Ontario greenhouse, that would be fine," he said.

According to the U.S Centers for Disease Control and Prevention, 167 people have been infected with the same strain of salmonella since mid-April. At least 23 people have been treated in hospital. Illnesses have been reported in Arizona, California, Colorado, Connecticut, Idaho, Illinois, Indiana, Kansas, New Mexico, Oklahoma, Oregon, Texas, Utah, Virginia, Washington, and Wisconsin.

Common symptoms of salmonella infection include nausea, vomiting, abdominal pain and diarrhea, although more serious consequences are possible, especially in children, the elderly and those with weakened immune systems.

With files from the Associated Press