New Delhi, July 24 -- WASHINGTON - Federal health authorities said Wednesday they are investigating a second cyclospora outbreak in the United States, with an unspecified food source and at least a dozen cases under investigation, as the first, far larger outbreak continues to generate new illnesses across more than a dozen states and defies resolution.

The Food and Drug Administration announced the new investigation without naming a suspected product, stating that a traceback procedure had been initiated to trace the contaminated food through the supply chain. The agency said the investigation was active and that additional details would be released as they become available. The new outbreak is distinct from the ongoing investigation in...