“Some weeks this year, 90 percent of applicants would test positive for something,” ruling them out for the job, said Laura Stephens, a human resources manager for the company in Denver.

The state’s unemployment rate is already low — 3 percent, compared to 4.7 percent for the entire nation. Failed drug tests, which are rising locally and nationally, further drain the pool of eligible job candidates.

“Finding people to fill jobs,” Stephens said, “is really challenging.”

Job applicants are testing positive for marijuana, cocaine, amphetamine and heroin at the highest rate in 12 years, according to a new report from Quest Diagnostics, a clinical lab that follows national employment trends. An analysis of about 10 million workplace drug screens from across the country in 2016 found positive results from urine samples increased from 4 percent in 2015 to 4.2 percent in 2016.