Three Roma women and a Roma man have been arrested on suspicion of carrying out 43 robberies in various parts of the country, including Athens, Thessaloniki and Volos, after drugging their elderly victims.
The suspects are alleged to have pretended to be promoting fruit juices, which were in fact laced with drugs.
They would rob any elderly people who drank the juice and lost consciousness.
A special police team was put together to catch the suspects and the arrests were made on Friday.
Two women, aged 40 and 42, were arrested as they drugged an 83-year-old woman in Patissia, central Athens.
The 40-year-old man and a 35-year-old woman were arrested later that day in Aghia Varvara, western Athens.
They were found to be in possession of various drugs and 50 sleeping pills, police said.