French authorities have launched a nationwide hunt for thousands of tiny Chinese-made telephones used by convicts to continue criminal activities from inside prison.

The telephones, no bigger than a cigarette-lighter, are almost entirely plastic, and have a reputation for being virtually invisible to metal detectors.

Under Operation Prison Break, announced on Tuesday by the cyber crime branch of the Paris prosecutor’s office, prison officers have been authorised to conduct searches in 500 cells in 66 detention centres.

According to Le Monde newspaper, the devices were nicknamed “suppositories” by prison inmates because of their ease of concealment.

“Investigations have established that some of these telephones were used to commit crimes from inside detention, including drugs trafficking, racketeering, arson and attempted murder,” a statement from the prosecutor’s office said.

The French supplier of the devices – a company called Oportik – has been stopped from trading and three staff members arrested. It is believed to have sold about 5,000 of the phones, the cheapest of which cost just €20 (£16.84).

France’s Justice Minister Gerald Darmanin has pledged to crack down on drug gangs and other criminal organisations, whose leaders he said are too often able to continue to conduct operating even after being jailed.

In 2024 some 40,000 mobile phones were confiscated in prisons. Conventional devices are projected over prison walls or dropped by drones. Others are smuggled in by corrupt prison staff. Phone-jamming is deployed in some jails, but there are doubts about its efficacity.

Similar mini-phones are manufactured in large numbers in China, according to Le Monde. While they are themselves perfectly legal in France, it is a crime to supply a prisoner with a phone.

The French prosecutor’s office said it had passed information on how it traced the Oportik phones to the EU’s judicial cooperation agency Eurojust, so that other countries can conduct similar clampdowns.