More employees tested positive for marijuana, methamphetamine and synthetic urine in first-quarter workplace drug tests, according to Diagnostic Laboratory Services Inc.

Marijuana use was up to 2.98% from 2.89% year over year, while amphetamine rose to 0.89% from 0.78%. Synthetic urine, used to disguise drug use, increased to 1.62% from 1.15%.

“We usually stay between 1.1% and 1.3% for synthetic urine, and suddenly we’re at 1.6%. There’s concern in looking at these numbers that people obviously are taking different drugs … that their employer doesn’t think is appropriate,” said Steven Brimmer, director of toxicology. “It’s not a good sign.”

Meanwhile, positive tests for cocaine fell slightly to 0.32% from 0.39% while opiate use fell to 0.18% from 0.19%, according to DLS, which typically samples 7,000 to 10,000 drug tests each quarter.