PROVIDENCE, R.I. (AP) — Investigators are reviewing hundreds of criminal cases in Rhode Island that could be undermined by the possible contamination of evidence at the state health department’s forensic chemistry lab, state Attorney General Peter Neronha said Friday.

Neronha said his office was notified of what he described as a “possible contamination event” on Tuesday. He said the incident potentially affects the results of drug-related evidence used by his office, specifically tests used to detect cocaine.

Neronha said the problem focused on tests by one laboratory scientist that may have yielded false positive results for cocaine. The forensics lab has identified 52 cases that are potentially impacted. Aother 263 cases are pending review.

Drug-related court evidence produced by other laboratory scientists — or evidence in which cocaine was not indicated — do not appear to be affected.

Neronha said he’s asked that all affected evidence be retested and that notices be sent to defense attorneys representing defendants and to police departments.

It doesn’t appear that any of the defendants who might be affected are being held solely based on charges involving cocaine, Neronha added.