"The scary part is, if we found 4,200, we know that's not all of them," Crews said.
And while prison officials are trying their best to keep cellphones out, it's not such an easy task. Jamming cellphone signals is prohibited by federal law, and it costs more than $1 million each for authorized towers that control what cellphone calls can come in and out of prisons. Some prisons even have to police their own corrections officers who sometimes help inmates receive contraband.
In Texas, a death row inmate made several calls with a cellphone to state Sen. John Whitmire, who chairs the Criminal Justice Committee. Whitmire didn't believe it when he started receiving calls from death row inmate Richard Tabler.
"He held his phone out, I guess outside his cell and there was a very distinct prison noise. He said, 'Did you hear that?' and I said, 'Yup. That's a prison,' " Whitmire said. "I said, 'How'd you get that phone?' He said, 'I paid $2,100 for it.' I said, 'How do you keep it charged?' He said, 'I have a charger.' "
The calls continued, and Whitmire had the phone investigated. The month before, Tabler used 2,800 minutes and was sharing the phone with other prisoners, Whitmire said. Tabler's mother, in Georgia, was paying the bill and collecting payments from the other prisoners' families.
Tabler asked Whitmire if he could help arrange a visit with his mother. When she arrived in Texas she was arrested for her part in the prison cellphone scheme. Tabler wasn't happy about that and made another call to Whitmire. "He said he was going to have me killed," Whitmire said.
In other cases around the country, infamous murderer Charles Manson, imprisoned in California, was found with a cellphone under his mattress, twice.
Two Indiana prisoners were convicted of using cellphones smuggled in by guards to run an operation that distributed methamphetamine, heroin and other drugs. A prisoner in Georgia was accused this year of using two cellphones to impersonate a sheriff's lieutenant and scam elderly drivers who had received red light camera tickets, getting them each to pay about $500.
In Oklahoma, a newspaper investigation found dozens of prisoners using cellphones to maintain Facebook pages. The Oklahoman found about three dozen inmates who were disciplined by prison officials and its reporters found about as many who hadn't been caught.
Florida prisoners have also been using social media with cellphones.
"We've got inmates running their own blogs and all kinds of stuff. We stop it when we catch it, but it's very difficult to police the whole Internet. We don't have Internet police on our staff," said assistant corrections secretary James Upchurch.
Those helping inmates smuggle phones into Florida prisons can be charged with a third-degree felony punishable by up to five years in prison. In Mississippi, the penalty can be 15 years for having a cellphone in prisons.
As corrections departments keep looking for new ways to stop cellphone smuggling, prisoners are finding creative, new ways to get them in.
"You may get a prepackaged, sealed ramen noodle soup — and it's completely sealed — the weight seems to be right, but when you open it, there's a cellphone inside," said Timothy Cannon, Florida's deputy corrections secretary. "They're very, very, very creative in the way they do some of these things."