SACRAMENTO (AP) — Nearly a quarter of inmates tested in a screening last year in California had used one or more illegal substances, leading state prison officials to propose increasing penalties for drug and alcohol use.

Under the recommendation, a first positive test for drug use would cost inmates 90 days’ pay from work assignments, and repeat offenses could mean up to year of lost wages.

However, inmates are paid only pennies an hour, prompting an official with the guards’ union to question the proposed regulations on Monday.

The department also plans to standardize mandatory drug testing across prisons.

While making its proposal, the California Department of Corrections and Rehabilitation said there were more than 4,000 drug-related prison incidents last year. More stringent penalties for drug use would increase prison safety and help inmates complete substance abuse treatment programs, the agency said.

“We recognize a problem with the use of drugs in our population, and the culture that it creates, and we must act to prevent the introduction of narcotics while providing treatment to those who are addicted,” department spokeswoman Kristina Khokhobashvili said in an email.

Nearly 23 percent of inmates tested positive for one or more illegal drugs during the screening in June of a quarter of the inmate population, the department said. The figure could be even higher since about 30 percent of the selected inmates refused to be tested, even though they were promised that no one would be punished for testing positive.

More than half the positive tests involved marijuana, 20 percent indicated morphine use; 14 percent methamphetamines; 11 percent amphetamines; and 2 percent cocaine.

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