Health officials in the United States say a test that appeared to identify the cause of an outbreak of explosive diarrhoea has turned out to be a false positive. The U.S. Food and Drug Administration (FDA) announced that the earlier finding was incorrect, meaning the exact source of the parasite responsible for the illness is still unknown. The outbreak, caused by a parasite, has affected many people across multiple states. Symptoms include severe diarrhoea, cramps, and nausea. The FDA had previously reported that the source might have been identified, but further testing showed that result was not reliable. A false positive means a test incorrectly indicated the presence of a specific contaminant. In this case, it led investigators to believe they had found the contaminated food product, but subsequent checks proved that was not the case. As a result, the investigation is ongoing. Health officials are now working to trace the actual source. They are collecting more samples and interviewing patients to find common foods they ate. The public is advised to practice good hygiene and wash fruits and vegetables thoroughly. Anyone with severe symptoms should seek medical care. The FDA has not released new details about which foods might be involved. They continue to urge caution and say they will provide updates as more information becomes available.