COLUMBIA, S.C. (AP) — Federal prisons officials on Wednesday tested a jamming technology inside the walls of a federal prison, a rare move that authorities said they hope will help combat the danger posed by inmates with cellphones.

The test was conducted over several hours Wednesday morning at a federal prison in Cumberland, Maryland, Assistant Attorney General Beth Williams told The Associated Press as the testing took place. Williams didn’t give specifics of how the test worked but said it marks a step in the fight to cut down on inmates’ ability to communicate unsupervised and carry on with criminal efforts.

Similar tests occurred in 2010, but Williams said Wednesday’s effort was significant because jamming technology has evolved, as have inmates’ efforts to smuggle in the devices. Such tests, she said, could lead to the broader use of technologies like jamming inside prisons to immobilize inmate phones, which officials across the country have described as their No. 1 security threat.

“Today is a big step, and the reason really is that, as criminals increase their capacity to commit crimes behind bars, we have to increase our capacity to stop them,” Williams told AP.

The renewed interest in jamming within federal facilities follows an announcement by Deputy Attorney General Rod Rosenstein, who told a national meeting of corrections officials that federal prisons would start testing the technology anew.

“That is a major safety issue,” he said in his speech. “Cellphones are used to run criminal enterprises, facilitate the commission of violent crimes and thwart law enforcement.”

The federal Bureau of Prisons, which houses 185,000 inmates, confiscated over 5,000 cellphones from inmates in 2016, Williams said, and preliminary figures show that number rose last year.

For years, officials in state and federal prisons have spoken out about the dangers posed by cellphones in the hands of inmates, who can use them to continue their criminal endeavors behind bars, including drug trafficking, extortion scams, and even hits on witnesses and others.

Last year, South Carolina Corrections Director Bryan Stirling testified at an Federal Communications Commission hearing in Washington alongside Robert Johnson, a former South Carolina corrections officer who was nearly killed in 2010 in a hit orchestrated by an inmate using an illegal phone.

In July, an inmate was able to escape from a maximum-security prison in South Carolina, thanks in part to a smuggled cellphone. Jimmy Causey was recaptured three days later in Texas.

A decades-old law says federal officials can grant permission to jam the public airwaves only to federal agencies, not state or local agencies. Telecommunications companies are opposed, saying jamming cell signals could set a bad precedent and interfere with legal cell users nearby.

Stirling, an outspoken advocate for some sort of technology to combat phones within prisons, wrote in June to Attorney General Jeff Sessions, beseeching the top prosecutor for help pursuing FCC permission to jam cell signals of the phones, which are thrown over fences, smuggled by rogue employees and even delivered by drone.

South Carolina Gov. Henry McMaster also lobbied, writing Sessions an August memo on the dangers of prison cellphones and thanking him for any help he could provide. That month, Williams also weighed in, writing in a letter to FCC officials that addressing the security threat posed by contraband cellphones “should be a chief priority” of both the Commission and Justice.

FCC Chairman Ajit Pai has signaled willingness to work on the issue, telling members of Congress he would put together a working group to address “the proliferation of contraband wireless devices in prisons and the potentially devastating implications for public safety.”

Williams said Justice, which oversees the Bureau of Prisons, was optimistic Pai and others at the FCC grasp the need for a way to fight the use of illegal cellphones.

“It’s my understanding that Chairman Pai really understands the threat here,” Williams told AP. “We need to do everything possible to prevent the threat from these phones being used.”

Stirling applauded Wednesday’s test, saying he and other state-level officials needed the ability to use similar technology in their institutions.

“South Carolina state prisons and local jails should be allowed to use the same tools to promote public safety as the federal government,” he said in a statement to AP. “We look forward to continued efforts to end this threat.”

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