OKLAHOMA CITY (AP) — Thousands of illegal cellphones are making it into the hands of prison inmates who use the devices to commit crimes, but prison officials testified Monday that they're prohibited from using one of the best tools to stop it — jamming technology.

Prison officials from Oklahoma and South Carolina testified about the effectiveness of cellphone-jamming technology before an Oklahoma Senate committee. Federal law bans the use of such technology by state agencies, and it is opposed by the wireless industry.

Oklahoma seized more than 5,200 contraband cellphones from inmates last ye...