Computer tablets thrown into grounds of jail
Stemming the flow of mobile phones and drugs has already been established as a key task for authorities as they attempt to improve safety levels across the system.
Now an inspection report has disclosed that tablet computers are among banned items discovered behind bars.
The assessment of HMP Haverigg, a category C male training prison in West Cumbria, said: "The greatest threats to security were phones and drugs.
"During 2016, a large quantity of banned items had been thrown over the perimeter fence, including computer tablets."
The report from HM Inspectorate of Prisons added that on several occasions intruders had breached the perimeter fence "to get closer to residential units".
Steps had been taken to counteract this evolving threat, the watchdog noted, including the cladding of fencing.
Chief Inspector of Prisons Peter Clarke said: "The long, rural and therefore vulnerable perimeter added to the problem of drugs at the establishment, and we were shown the evidence of some significant finds."
The availability of electronic devices in prisons has emerged as a major problem for ministers and governors in recent years.
Figures published by the Ministry of Justice last month revealed that 13,000 mobile phones and 7,000 sim cards were recovered in jails last year.
There have been warnings that criminal gangs are using handsets to organise the trafficking of drugs into prisons, to "terrorise" victims and to post on social media.
HMIP concluded that Haverigg had a troubled past but was making improvements.
Mr Clarke said there was still much to do at the establishment.
"That said, we recognise the efforts made by the governor and his team not to let that troubled past define the prison's future," he added.