Fewer than one in 500 prisoners reported being sexually abused or harassed in Maryland prisons last year ? a figure believed to be well short of the actual number of sexual attacks, according to a government study released Sunday.

Out of more than 23,000 inmates in Maryland prisons in 2005, only 15 reported a nonconsensual sex act by an inmate and one reported a case of sexual abuse. Seventeen reported staff sexual misconduct with inmates, the study states.