WASHINGTON (AP) — The government said Thursday that the salmonella outbreak that sickened at least 1,440 people appears to be over, but its ultimate source may never be known, partly because of shortcomings in the nation's food safety system.

The Centers for Disease Control and Prevention and the Food and Drug Administration said they found strong evidence to implicate jalapeno and serrano peppers, and a farm in Mexico, in the largest outbreak of foodborne illness in a decade. Investigators were unable to clear domestic and imported tomatoes, however, although the evidence against tomatoes is weaker.

The FDA also lifted its warning that consumers avoid eating jalapeno and serrano peppers from Mexico. But officials pointedly said that doesn't guarantee another such outbreak can be prevented.