One-third of all drug tests on drivers killed in motor vehicle accidents came back positive for drugs ranging from hallucinogens to prescription painkillers last year, according to a National Highway Transportation Safety Administration report released Tuesday.

The report, the agency's first analysis of drug use in traffic crashes, showed a five percentage point increase in the number of tested drivers found to have drugs in their systems since 2005 -- from 28 percent to 33 percent. The increase coincided with more drivers being tested for drugs over that period, the report shows.

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