Police arrested 21 suspected triad members and a woman following a standoff between two rival gangs outside a restaurant in Yau Ma Tei. Police said suspected members of the Wo Shing Wo triad society were stopped by members of the Wo On Lok triad gang as they left a wedding banquet at a Jordan Road restaurant at about 11.30pm on Sunday. 'Preliminary investigation revealed that the incident was sparked by a debt,' a police source said. Officers arrested 21 males, aged from 16 to 52, for unlawful assembly. A woman, 39, was also arrested for obstructing police.