Update at 4.30pm: The Singapore Civil Defence Force has established that the suspicious substance found at Woodleigh MRT station is baking flour, according to a tweet by the police. The MRT station has since resumed operations following a three-hour closure.
A 69-year-old man who left the substance there has been arrested for causing public alarm.
Two other men aged 53 and 70 are currently assisting with police investigations.
A suspicious substance was found on Tuesday afternoon (April 18) at Woodleigh MRT Station.
The station is temporarily closed, according to updates on the Singapore Police Force's official Facebook page.
SBS Transit also announced on its Twitter page that the station is closed "due to a security incident".
Free bus rides are available at bus stops between Serangoon and Potong Pasir stations, said SBS Transit on Twitter.
Said the police in a later update, officers from the Singapore Civil Defence Force's (SCDF) hazardous materials (HazMat) team are also at the scene attending to the incident.
Police have advised members of the public not to speculate on the incident.
Earlier this month, Hougang station was also closed due to security concerns. A 39-year-old man had left a bag unattended at the station and was subsequently arrested by the police.