Greek police say they have foiled a plot by inmates to smuggle drugs and cellphones into a prison using a drone operated by accomplices outside.

A police statement Friday said four Albanian prisoners — including one who was out on a furlough and has been arrested — will be charged with drugs offences and running a criminal gang.

Another two people were taken into custody for allegedly preparing to smuggle the drugs into the prison. Police found the drone, 200 grams (7 ounces) of heroin and 400 grams of marijuana in their possession, as well as 16 mobile phones.

The statement said the prisoners had been planning to sell the drugs and phones to other inmates, and were likely to have made about 150,000 euros ($170,000) out of the venture.