Employees testing positive for marijuana use continued on an upward trend in the second quarter of the year, according to statistics released by Diagnostic Laboratory Services.

From April through June, 2.5 percent of the drug tests conducted on workers tested positive for marijuana, the report said. In the first quarter of the year, 2.3 percent tested positive, while a little more than 1.5 percent of the tests came back positive in the second quarter of 2007, the report said.

Drug use in other categories remained stable, the report said.

"There's a slight uptick in opiate use, but cocaine use is slightly down," said Carl Linden, DLS scientific director of toxicology. "While amphetamine use remains the same at a relatively low percentage of 0.6 percent, it is still roughly three times higher here than on the Mainland."

The company, which describes itself as Hawai'i's largest drug-testing company, releases drug statistics each quarter. The company handles drug testing for about 800 local businesses and the quarterly sample size typically includes 7,000 and 10,000 drug tests.