OTTAWA -- Criminals who run their operations from behind bars using mobile devices could soon be left searching for cell service.

The federal government is asking companies how to stop prisoners from making calls on smuggled cellular and smart phones, tablets and other wireless devices.

Such devices are banned in jails -- but evidently, that hasn't stopped prisoners from getting hold of them.

"Though this prohibition is rigidly enforced, upon occasion, mobile devices are recovered by correctional officers from inmates within an institution," says a notice posted Tuesday on a government contracts website.

"It is, therefore, of significant importance for (the Correctional Service of Canada) to develop an effective and sustainable method of preventing the use of mobile devices by inmates in support of its public safety mandate. To that end, CSC seeks a solution to impede the use of contraband mobile devices within the confines of correctional institutions across Canada."

The notice gives no indication about the extent of the problem in Canadian prisons.

But a Correctional Service spokeswoman says 120 cell phones were confiscated nation-wide in 2010-11, up from 94 in 2009-10 and 51 in 2008-09.

"Similarly to other forms of contraband, cell phones can and have been smuggled into institutions in offender personal effects, by inmate visitors and some staff/contractors, by inmates in their body cavities, hidden in deliveries to the institution via supplies and or the kitchen, and in throw overs just to name a few," Veronique Rioux said in an email.

A written government response to a recent report by the House of Commons public safety committee sheds further light on the issue.

"Despite current efforts, cell phones continue to serve as a conduit for inmates to engage in criminal activities, both inside and outside penitentiary walls," says the government's letter to the committee's chair, Conservative MP Kevin Sorenson, dated Aug. 8.

The letter lists some ways jails try to keep out mobile devices, such as searches of inmates and visitors, X-ray baggage scanners and metal detectors.

"While detection and prevention tools are useful, each has limitations and despite continued efforts to detect and seize these devices, rendering these devices ineffective may prove to be the most effective means of disrupting these criminal activities," it says.

One avenue being explored is signal-jamming technology, which is banned in Canada because it can block emergency calls. Both the government's letter and the notice posted Tuesday indicate an openness to signal-jamming tools, provided they don't interfere with 911 calls.

Companies have also been asked if technology exists that would allow corrections officers to power off prisoners' phones or to make them ring so guards can find them more easily.

Smuggled cell phones are a hot commodity in American prisons. The U.S. Federal Bureau of Investigation says authorities confiscated 2,800 mobile devices in California jails alone in 2008 and the problem is only getting worse.

Prisoners were found to be using the devices to intimidate and threaten witnesses, send offensive photos to victims, orchestrate crimes, co-ordinate escapes, bribe prison guards and order retaliation against other inmates, the two-year-old FBI report says.

The FBI cited one instance in which a correctional officer reported earning more than $100,000 by charging prisoners $100 to $400 per device. Prisoners were found to be charging each other up to US$50 for each call, the report adds.

"At one time, drugs and tobacco served as the contraband of choice by prisoners," the FBI says. "Now, wireless phones are becoming popular."