SINGAPORE - A 69-year-old man has been arrested after he left a suspicious white substance at Woodleigh MRT station, the police said on Tuesday (April 18) evening.

In their statement, the Singapore Police Force said the man was arrested for an offence of public nuisance after his actions, which triggered a temporary closure of the MRT station for about three hours.

The police added on Tuesday night that two other men, aged 53 and 70, were assisting with police investigations.

They were together with the man who left the flour at Woodleigh MRT Station, preliminary investigations showed.

The flour was used to mark a trail for their running route, the police said in a news release.

Police were alerted to the incident at about 1pm. Singapore Civil Defence Force's (SCDF) HazMat officers subsequently established the substance to be baking flour.

The police said they take all security threats seriously and will not hesitate to take action against anyone who causes public alarm.

They also reminded the public to report any suspicious items or behaviour to the police or transport authorities immediately.

The suspicious white substance at Woodleigh MRT station was found by a cleaner, said MP Melvin Yong.

Mr Yong, who is also executive secretary of the National Transport Workers' Union (NTWU), added that the cleaner "did a good job in identifying a potential threat, taking responsibility and raising the alert".

"It is not easy and often we take our security for granted," he said in a Facebook post.

The station resumed service at 4.20pm, police said in an update on their Facebook page.

It was closed at around 1.25pm after staff from SBS Transit, which operates the North-East Line, spotted a white substance in the station.

Officers from the Singapore Civil Defence Force's (SCDF) hazardous materials (HazMat) team were deployed at the scene.

SBS Transit first tweeted about the closure due to a "security incident" at 1.49pm. The police then said that a suspicious substance had been found.

Free buses at bus stops between Serangoon and Potong Pasir stations were activated by SBS Transit during the incident.

The police, which updated the public of the situation via several posts on its social media accounts, advised members of the public not to speculate on the incident.

Potong Pasir MP Sitoh Yih Pin, speaking to reporters after the station reopened, said it was not an overreaction to close the station, as "you must not take chances in situations like this".

During the closure, Mr Sitoh - along with grassroots volunteers - stationed himself at the station's bus stop with umbrellas to ferry commuters as it was raining heavily. A part of the sheltered walkway had been blocked off temporarily.

Mr James Lee, a commuter at the station when it reopened, said he was not worried even though he heard there was an incident earlier.

"I believe the authorities are prepared to deal with instances of suspicious substances speedily," he said.

The closure follows a similar incident on April 2, when Hougang station was briefly shut down due to security concerns over an unattended bag.

A 39-year-old man was arrested for an offence of public nuisance.