Oklahoma health officials are investigating an outbreak of salmonella in several schoolchildren and some adults and say it may be connected to similar outbreaks in Iowa and Nebraska.

A total of 16 cases in three counties have been identified involving at least four elementary schools, according to Leslea Bennett-Webb, spokeswoman for the Oklahoma Department of Health.

No one has died, although one adult has been hospitalized due to the strain of Salmonella Java that can cause bloody diarrhea, abdominal cramps, fever and vomiting.

We don't know yet ... what is the vehicle. That is something we're still trying to study, said Bennett-Webb.

We are beginning to think we might have something a little different than our usual salmonella outbreaks. It really is a puzzle.

The cases have been reported in different parts of the state, she said.

Previous U.S. salmonella outbreaks have been linked to peanut butter and contaminated produce, and recently a large salmonella outbreak has been linked to contaminated eggs, forcing the recall of more than half a billion eggs.

About 2,000 people were reported sick with salmonella in the United States from May to July, almost triple the norm.