An investigation of corrosion testing conducted on the trans-Alaska pipeline concluded that a contractor used inexperienced and poorly trained workers. But the probe found no firm evidence of drug use on the job.

The four-month investigation was carried out by the Federal-State Pipeline Monitoring Office in Anchorage. The findings were announced Monday.The investigation looked into corrosion testing performed in 1990 by Thorpe Technical Services Inc. for the Alyeska Pipeline Service Co., which operates the 800-mile pipeline for major oil companies, including Exxon, BP and Arco.

The probe by the U.S. Bureau of Land Management, the Alaska Department of Natural Resources and the U.S. Transportation Department turned up no significant new corrosion problems and no "federally indictable evidence" of drug use.