Anonymous urine samples collected from truck drivers during safety inspections in Salem, Ore., revealed that 10 percent of drivers tested positive for drugs, the Oregon Statesman-Journal reported May 3.

The state police said "Operation Trucker Check," conducted over a three-day period, involved 500 truckers. Marijuana, methamphetamine, and opiates were the most commonly detected drugs. However, officials did not determine whether any of the drugs were being used legally; some of the 16 drivers who tested positive for opiates, for example, may have been legally using drugs like Vicodin.

"It's a problem bigger than enforcement and state police," said Oregon state police Sgt. Alan Hageman. "It needs to be looked at by the transportation community as a whole."

"We continue to be concerned by any drug use by our drivers. Our industry has a zero tolerance, and that's our goal," said Bob Russell, the president of Oregon Trucking Association. Federal law requires truckers to submit to pre-employment and post-accident drug tests, but not random testing.

Officials said marijuana and methamphetamine use were found to be higher in the most recent safety check than in others conducted in 1998 and 1999.