MADRID (AP) — Spanish police have broken up a human trafficking ring that forced Chinese women into prostitution in Spain.

The gang approached the women in China and promised them well-paying jobs in Europe, Police Commissioner Carlos Rio-Miranda Iglesias said Tuesday.

Each woman paid the gang between 8,000 and 10,000 euros ($9,100-$11,400). After being flown to Spain, however, they were told they had a debt to the gang, held in unhygienic conditions in apartments and forced to work as prostitutes 24 hours a day, Rio-Miranda Iglesias told a press conference.

The gang took away the women’s passports and anyone who opposed the gang’s demands was drugged, he said.

The apartments were in the Spanish capital of Madrid and the northern Spanish cities of Zaragoza and Bilbao.

Police acted on a tip-off and arrested 63 people, including 60 Chinese citizens, two Spaniards and a Pakistani.

The alleged ringleader in Spain was a Chinese woman, although the gang’s true bosses are believed to be in China, police said.