Orlando, Fla. ? A salmonella outbreak at Walt Disney World sickened as many as 141 people, including visitors attending an athletic competition for organ-transplant recipients, health officials said Friday.

Eighteen cases were confirmed by laboratory tests. However, the Centers for Disease Control and Prevention in Atlanta estimates 141 people who attended the U.S. Transplant Games in late June may have gotten sick.

The outbreak source was prepackaged, diced Roma tomatoes served at six Disney World restaurants, Orange County epidemiologist Bill Toth said.

The restaurants stopped serving the tomatoes immediately, Disney spokeswoman Marilyn Waters said.

Salmonella can cause diarrhea and fever. More serious infections can occur in children, the elderly and people with weak immune systems, such as organ transplant recipients.

After two people who attended the U.S. Transplant Games became sick, the CDC traced the source by asking people about their eating habits during the competition, Toth said. Of the 369 who responded, 82 reported being sick.

No deaths were reported.

Because transplant recipients are more susceptible to infections than the general population, the CDC suggested that doctors place transplant patients who may have salmonella on antibiotics.