A lettuce sample linked to a multi-state Cyclospora outbreak was found to have produced a false positive result, according to the U.S. Food and Drug Administration.

Despite the error, Taylor Farms’ voluntary recall of iceberg lettuce from Mexico remains in place while officials continue investigating the outbreak.

The recalled lettuce had been distributed to retailers and used by Taco Bell locations in several states, prompting the chain to stop using the supplier.

The FDA said there are currently no confirmed positive product tests for Cyclospora, which can cause severe diarrhea and other symptoms, NBC News has reported.

Experts noted that testing for the parasite is difficult and that false positives can occur, but praised the recall as a precautionary step.