State public safety officials say the backlog of drug evidence testing caused by a shutdown of two state labs will take more than two years to erase.

The officials told the House Ways and Means Committee Wednesday that the backlog will take time to erase even with a major staff expansion, and it is growing by about 1,000 cases each month while the state works to develop new lab capacity.

The Telegram & Gazette reports that about two dozen senators and state representatives attended the hearing at Worcester State University.

A lab in Boston was closed last year after a chemist was accused of falsifying results. An Amherst lab was closed this year after a worker was charged with stealing drugs.