The U.K.'s Ministry of Justice has started to use "specialist mobile detection technology" to find and then seize phones that are being used illegally by prisoners.
The technology is being used to tackle the problem of mobile phone smuggling, which authorities said resulted in both violence and drug-dealing inside prisons.
When it detects the presence of a cell phone in prison, the technology sends real-time alerts. A digital heat map is used to identify the strength of the phone's signal, enabling prison officers to home in on its location "to the exact cell."
Prison staff are able to look at the data of a specific period of time to monitor the emergence of any patterns, such as when prisoners work together to smuggle drugs into a prison. The intelligence can be analysed and lead to arrests.
The technology has undergone a six-month trial in one prison and is being rolled out to four more facilities. The locations of where it's being used have not been made public.
"As criminals look for new ways to smuggle contraband into prisons, it is vital that we stay one step ahead, and this kind of technology will help prevent them operating from their cells," David Gauke, the U.K.'s justice secretary, said in a statement Sunday.
"This is vital to ensuring prisons are places of safety and rehabilitation, where offenders can turn their backs on crime for good," Gauke added.