Taiwan and the mainland have jointly busted two people-trafficking rings that sent mainland women to the island as prostitutes. The operation took place simultaneously in northern Taiwan and Fujian province on Monday, the mainland's Ministry of Public Security said yesterday. Police arrested 50 suspects and freed 21 mainland women. Acting on a tip from Taiwan's immigration department in February, police in Fujian spent five months investigating the rings. They were allegedly headed by Taiwanese nationals Wang Chun-hsiang and Lee Ming-lung, the ministry said. Police suspect the victims were told the gangs could arrange marriage to Taiwanese men. But after the women were sent to the island, Taiwanese gangsters forced then to work as prostitutes, the ministry said. Taiwan sent immigration officials and police officers to work alongside their mainland counterparts late last month and plan the raid. The two sides launched their operations at the same time on Monday, with mainland authorities arresting 30 people, including 26 from Taiwan. Taiwan's National Immigration Agency said 20 Taiwanese suspects were arrested on the island, including a crime boss identified as Chueh Kuang-cheng. Twenty-one mainland victims were rescued. The two rings were believed to have made more than NT$30 million (HK$7.9 million), raking in more than NT$570,000 in July alone, mainland police said. The crackdown was hailed as a milestone in cross-strait co-operation targeting the sex trade. 'This is the first joint operation by the law-enforcing departments of the two sides in busting women-trafficking and forced prostitution across the Taiwan Strait,' said a police spokesman from the mainland's ministry. The spokesman said the operation demonstrated the ability of law enforcement officials on the two sides to exchange information, gather evidence and co-ordinate simultaneous actions. The mutual assistance mechanism was established in April 2009, after mainland-friendly Taiwanese President Ma Ying-jeou took office in May 2008.