COLUMBIA, S.C. (AP) _ A drug analyst at the Columbia Police Department has resigned amid concerns over some of the work she did on cases while working for the agency.

Columbia Police Chief William Holbrook said at a news conference Monday that Brenda Frazier had submitted her resignation.

An audit by the Richland County Sheriff's Department found inconsistencies in Frazier's work and raised concerns about her training and methodology. Holbrook closed the lab last week, and the State Law Enforcement Division is now handling drug case testing for the city.

Frazier handled nearly 750 cases over the past three years. Holbrook says more than 180 of those are being reviewed.