Burger King Holdings Inc. said Thursday that some of its restaurants began receiving new shipments of tomatoes after a food poisoning scare forced the company to pull the produce nationwide.

The tomato shipments were expected to start Thursday at some of its locations, but company spokesman Denise Wilson said it could take weeks to restock the entire chain.

Federal authorities still haven't determined the source of the illness outbreak. As of Thursday, the toll from salmonella-tainted tomatoes had jumped to 228 illnesses in 23 states.

The government has said it's possible the food poisoning also contributed to the death of a cancer patient in Texas.

Florida and five other states that had escaped the outbreak so far were added to the affected list Thursday.

McDonald's Corp., the world's largest hamburger chain based in Oak Brook, Ill., said the company would continue to avoid serving sliced tomatoes on its sandwiches until it's able to source tomatoes that meet its food safety and quality standards and until there are enough to supply the whole chain.