Madrid, Oct 18 (IANS/EFE): Seventeen people have been arrested as suspects in the biggest jewellery heist in Spain's history, police said Thursday. The December 2012 theft in Madrid involved wristwatches valued at more than 23 million euros (about $31 million)

Among those arrested is a known thief, Ismael A.V., alias "The Troll", who is considered to be the mastermind of the heist.

It theft was carried out when the thieves gained access in December 2012 to the Diarsa company, where they robbed two safes, making off with more than 1,700 watches of prestigious Swiss brands.

Among the people arrested are 11 Chinese citizens, and more than 300 of the luxury watches have been recovered, some of them valued at almost 270,000 euros (about $368,000).

With the cooperation of Interpol, authorities have been able to locate more watches in Shanghai, where the organisation was selling them on the black market.

The criminals had entered the firm during working hours and gained access to the heavily armored room where the watches were kept without leaving any trace and without the guards detecting it, remaining inside carrying out their heist for four hours.

The thieves took with them the videotapes from the security cameras and knew the safe's combination, but - at the present time - police are ruling out implicating anyone working for the firm that was robbed.