ST. PAUL, Minn. (WCCO) – A crime lab controversy could force prosecutors in three Twin Cities counties to drop cases against drug suspects.

Questions came to light last month about how the St. Paul Police Department tested evidence.

One expert said the lab’s drug tests were insufficient and done by untrained analysts. On Wednesday, the Ramsey, Dakota and Washington county attorneys asked the state crime lab to re-test all the drug samples in pending cases.

They’ll start with cases where people are already being held in jail. Prosecutors say if there’s not enough evidence, charges could be lessened or dropped.

As for people who say they’ve already been wrongfully convicted, the county attorneys say they’ll review those accusations on a case-by-case basis.

Drug tests at St. Paul’s crime lab have been suspended for now.