Serangoon residents were startled by blasts that sounded like explosions last Friday night.
The sounds occurred about two minutes apart, shortly before 11pm.
One resident, 45-year-old purchaser Zhu Mei Zhen, told Chinese daily Lianhe Wanbao that she thought someone had fallen from a height when she heard the first noise at about 10.45pm.
Ms Zhu said she saw two young people, who appeared to be teenagers, place a box near the rubbish chute of Block 413, Serangoon Central, just across the road from Nex mall. The box later "exploded", causing the second bang.
Police later cordoned off the area around the rubbish chute. No injuries or damage to property were reported.
The Singapore Police Force said they were alerted to a case of "intentional alarm" at 10.50pm last Friday night, and that they were looking into the matter.
The Singapore Civil Defence Force said that the incident was a "false alarm", as no explosion had occurred.
Last month, two MRT stations were shut due to security scares.
On April 2, the Hougang station was closed for 20 minutes after staff found an unattended bag left behind by a 39-year-old man while he ran an errand. He was later arrested.
And a "suspicious substance" - later found to be baking flour left by a running group to mark a route - was found in Woodleigh station on April 18, leading to a three-hour closure. One member of the group was arrested, while another two assisted in investigations.