A man suspected of being a senior member of the Sun Yee On triad gang was arrested yesterday, the seventh day of a police crackdown triggered by last week's attacks on New World Development properties. The middle-aged man led officers from the Organised Crime and Triad Bureau - which is investigating the New World Development attacks - to the offices of the Hong Kong Muay Thai Association in Companion Court, Austin Avenue, Tsim Sha Tsui, to assist in a search. Two computers, three baskets of files and a suitcase were seized at the premises. Kowloon West regional crime unit officers also arrested 12 men and two women and seized HK$880,000 in cash and chips at a gambling den in Sham Shui Po allegedly controlled by Sun Yee On. And last night police raided a drug den linked to the triad in Sham Shui Po and arrested eight men and four women. Officers seized 16 grams of the drug Ice. Police have linked last week's attacks on the New World Development headquarters in Central, two hotels and vandalism against 16 mobile phone shops to Sun Yee On. 'We want to send out a clear message that we will never tolerate any challenge to law and order,' a police source said. 'Our operation targets the source of their income and cracks down on illegal activities controlled by their high-ranking members.' On Saturday, nine men with suspected links to the triad society were arrested in connection with the attacks, three of them while trying to leave for Shenzhen. All nine have been released on bail without charge. Referring to the first Sham Shui Po raid, a police source said: 'One of the male suspects is an office-bearer of Sun Yee On triad society. Investigation showed the den served high-ranking triad members and its daily turnover reached HK$2 million.' Last night, the suspects were being held for questioning but no one had been charged.