The ringleader, a 57-year-old Thai woman, was arrested at Zurich airport in October 2014, Bern police said in a statement on Monday.
Finally concluded after several years' work, the investigation found that since 2011 the ringleader had organized and paid for some 80 woman, mainly from poor families in Thailand, to come to Switzerland often “under false pretences”.
The women were taken to various different brothels in the cantons of Bern, Solothurn, Lucerne, Basel-City, St Gallen and Zurich and then forced to work as prostitutes to pay off their “travel debt”.
They were told to give all their earnings to the brothel managers, who kept half for themselves. The other half went towards paying off their ‘debt' of between 25,000 and 30,000 francs, said police.
The women were strictly monitored and could not move about freely outside the brothel.
The 57-year-old ringleader is currently in prison, said police.