Following a salmonella warning from the Food and Drug Adminstration over the weekend, McDonald's, Subway and other restaurants nationwide have temporarily stopped serving sliced tomatoes.

Burger King is serving tomatoes only in parts of California that are able to use risk-free sources.

Consumers should be careful, the FDA said Saturday.

Certain types of raw red tomatoes have been linked to cases of salmonella in 16 states, from California to Virginia, the FDA reported Saturday.

Pennsylvania, New Jersey and Delaware were not among the states that had reported cases, according to the FDA.

Consumers, however, can't be sure that Roma, plum or round tomatoes are safe unless they're definitely from Arkansas, California, Georgia, Hawaii, North Carolina, South Carolina, Tennessee, Texas, Belgium, Canada, Dominican Republic, Guatemala, Israel, Netherlands, and Puerto Rico, the agency said.

Safe to eat are cherry tomatoes, grape tomatoes, and tomatoes sold with the vine attached.

The situation is so complex, some restaurants have decided to be extra safe and pull sliced tomatoes from their menus.

"McDonald's is temporarily not serving sliced tomatoes on any of our sandwiches across the United States," according to a statement from the fast-food chain. "This is a precautionary measure only. McDonald's has not experienced any related issues to date. We will continue to serve grape tomatoes in our Premium Salads as the FDA indicates there are no issues with grape tomatoes."

"We stopped serving tomatoes Saturday night," said Subway spokesman Kevin Kane. "... That was nationwide." Earlier in the week, the chain had stopped serving sliced tomatoes in Texas and New Mexico, because of an FDA recommendation.

Subway, which has 22,500 restaurants in the United States, is trying to get a sufficient supply of tomatoes from FDA-approved locations, he said.

"In some restaurants we have be able to have them as early as tomorrow," he said. "It's something that we hope gets resolved quickly."

Burger King is also avoiding sliced tomatoes in "all of Canada, Puerto Rico and some restaurants in the Caribbean Islands, including Aruba, Freeport, Nassau, Grand Cayman, Curaçao and St. Maarten," according to a company statement.

WaWa in Wayne and East Goshen Township weren't putting tomatoes in sandwiches yesterday, two customers said.

The Wendy's in Haddon Township didn't even get sandwich tomatoes today, according to a manager on duty. Grape tomatoes are still being added to salads.

Since mid April, 145 cases of illness from salmonella, including 23 that were treated in hospitals, have been reported in 16 states, including Arizona, California, Colorado, Connecticut, Idaho, Illinois, Indiana, Kansas, New Mexico, Oklahoma, Oregon, Texas, Utah, Virginia, Washington, and Wisconsin.

Salmonella poses the greatest dangers to young children, the elderly, and people who are frail or have weakened immune systems. In healthy persons, symptoms can include fever, diarrhea (sometimes bloody), nausea, vomiting and abdominal pain, according to the FDA.

Contact staff writer Peter Mucha at 215-854-4342 or pmucha@phillynews.com.