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.
Two other men aged 53 and 70, are assisting with investigations. The Straits Times understands that the trio are part of the Seletar Hash House Harriers, a running club set up in 1980, with 82 members on its Facebook page.
In hashing, runners usually set a course by marking out a trail through the jungle, Housing Board estates and even in the city, using white flour, toilet paper or chalk marks. The groups are most common in former British colonies. In 2007, a hash group sparked a bioterrorism scare in the United States when two people sprinkled flour in a carpark for their run.
Yesterday's security incident was the second such occurrence this month. Hougang MRT station was closed for 20 minutes on April 2 after staff found an unattended bag. A 39-year-old man who left it was arrested for causing a public nuisance.
In yesterday's incident, a cleaner found the powder and an SBS Transit station manager alerted the police. The Singapore Civil Defence Force's hazardous materials team was also deployed. The public was advised to avoid the area and free buses operated between Serangoon and Potong Pasir stations.
Experts said that in view of the heightened security threat, the authorities' response was appropriate.
"We do know that train stations are targeted," said Dr Kumar Ramakrishna, head of policy studies and coordinator of the national security studies programme at the S. Rajaratnam School of International Studies. "It is due diligence on their part," he said, adding that baking flour could be a reminder of anthrax scares in the past.
Dr Rohan Gunaratna, head of the International Centre for Political Violence and Terrorism Research, said that chemical and biological agents have been used in the past in this region, such as by North Korean agents in Malaysia recently.
"Every security incident should be investigated," he said.
Professor David Chan, director of the Behavioural Sciences Institute at Singapore Management University, said such incidents are likely to occur again and people "should not be complacent nor be afraid to report any suspicious item or behaviour".
While the Woodleigh case caused some confusion among commuters, they said they had confidence in the authorities' ability to deal with such situations. Commuter James Lee, 38, who was at the station when it reopened, said he believes the authorities are prepared to deal with security incidents speedily.
Meanwhile, Potong Pasir MP Sitoh Yih Pin stressed that it had not been an over-reaction to close the station, as Singapore must not take chances in situations like this.
