The authorities seized just over 100 tonnes of copper as part of the operation carried out at “El Gallinero”, or “The Chicken Coop”, a squatter settlement on the outskirts of Madrid that is home mainly to Roma migrants.

“This area of Madrid served as the headquarters of one of the most active copper theft groups that operated across the country,” police commander Javier Rogero told reporters.

“The theft of copper is taking place practically in all geographic areas but thanks to operations like this one we are managing to slowly reduce their numbers.”

Most of the copper stolen by the gang came from water pipes and telephone lines, but some of it was stripped from high-speed rail lines.

With prices hitting a record of 8,966 dollars per tonne earlier this month because of strong demand from countries like China, copper bandits around the world are reaping the benefits of a market fighting to keep up with demand.

The industrial metal, which is used in plumbing, heating, electrical and telecommunications wiring, has rocketed by around 50 percent since June, boosted also by the weak dollar and strikes in key producer Chile.