The Food and Drug Administration (FDA) has found Cyclospora in Florida irrigation canals, as part of its investigation into the source of a major multistate outbreak in the U.S.

Nearly 700 people have been sickened, including 37 who have been hospitalized, amid an outbreak that has been linked to Fresh Express salads.

The FDA said its traceback investigation identified "several farms" in the U.S. that may have provided product used in the Fresh Express salads that were recalled.

"In Florida, FDA analyzed water samples from two public access points along a regional water management canal (C-23), located west of Port St. Lucie, Florida.

"These samples tested positive for Cyclospora cayetanensis using FDA’s validated testing method."

However, it wasn't able to determine if the Cyclospora detected in the canal is a genetic match to the clinical cases, given the emerging nature of genetic typing methodologies for this parasite.

Therefore, there is "currently not enough evidence to conclusively determine the cause of this outbreak".

But it said that the current state of the investigation "helps advance what we know about Cyclospora and offers important clues to inform future preventive measures".

FDA is working with the state of Florida and the local water district in the area to try to determine the source and impact of Cyclospora in the canal.

As of August 14, the Centers for Disease Control (CDC) is reporting a total of 690 cases across 13 states.

FDA’s traceback investigation is complete, but the cause or source of the outbreak has not yet been determined via traceback. Based on the traceback, carrots are no longer being investigated for this outbreak. Two of the salad ingredients, red cabbage and iceberg lettuce, continue to be items of interest in the investigation.