Billowing smoke that spread alarm at an underground train station in central Singapore on Monday was apparently caused by a technical fault, media reported.

Authorities have called for vigilance since Indonesian police arrested six suspected Islamist militants on Aug. 5 on suspicion of plotting an attack on Singapore.

Videos on social media showed commuters rushing out of a train at the Tanjong Pagar station, covering their noses to protect themselves from gray smoke. Some of them were seen taking pictures on their phones. Continue reading.