A 69-year-old man who used flour to mark a trail for a running route was arrested for causing public alarm yesterday, when the substance was found at several spots in Woodleigh MRT station. The station was closed for around three hours, reopening at 4.20pm, after the authorities ensured the white powder was not dangerous. SMU Behavioural Sciences Institute Director Professor David Chan said such incidents are likely to occur again and people "should not be complacent nor be afraid to report any suspicious item or behaviour".