(AP) — Food safety advocates are sounding an alarm at the lack of information being disseminated about an enduring intestinal illness tied to prepackaged salad that has sickened nearly 400 people nationwide.

The outbreak of the rare parasite cyclospora has been reported in at least 15 states, and federal officials warn it is too early to say it is over.

But if you’re looking to find out exactly where it came from, you may be out of luck.

Health officials in Nebraska and Iowa say they’ve traced cases there to prepackaged salad. But they haven’t revealed the company that packaged the salad or where it was sold.

The lack of information has fueled concern from critics say information about the outbreaks is crucial for consumers.