PARIS  -  French authorities on Tuesday launched a major operation to crack down on the use of miniature mobile phones in prisons nationwide, searching 66 jails across the country in a bid to seize thousands of the devices.  The operation, called “Prison Break”, aims to seize “miniature telephones put into circulation by a Chinese company and resold in France”, said Paris prosecutor Laure Beccuau.

The raids come after the use of the devices was blamed for lawlessness in prisons, with detainees still masterminding drugs deals and even contract killings while behind bars.

Searches for the 5,000 such phones estimated to be on French territory had been authorised in some 500 cells, the prosecutor said.

She said that the phones -- the size of a cigarette lighter -- had been resold by a French supplier called Oportik whose website has now been blocked by the authorities after its domain name was seized.

The prosecutor emphasised it was against the law to give any kind of mobile phone to a detainee.

The devices are marketed as being undetectable by security at the entrances to jails.

“Investigations have established that some of these phones have been used to commit drug trafficking offences, fraud, damage to businesses by fire and attempted murder from inside prisons,” said Beccuau.

France’s right-leaning government has been under pressure to restore security in prisons after convicted drug trafficker Mohamed Amra, known as “The Fly”, escaped detention in May last year.

The tightly coordinated breakout left two prison officers dead.

Amra was finally arrested in Romania after evading arrest for nine months and extradited to France.

Last month, a series of coordinated attacks affected French prisons. Cars were torched, there was automatic gunfire and mysterious inscriptions were left behind.

Prosecutors blamed the attacks on drug traffickers.