Authorities held meetings with residents in the area on Sunday, informing them of the situation.
When CNA arrived at the scene on Monday at about 2pm, at least 30 Singapore Armed Forces (SAF) personnel were seen working on site.
A barrier made of concrete blocks was being built around the bomb. Officers were also seen carrying sandbags into the construction site.
Police vans arrived at Hazel Park condominium at about 4pm, with officers in vests arriving to survey the area.
In a letter seen by CNA, residents were told to leave their homes before 8am on Tuesday and to stick a green strip of paper on their front door when they vacate. This green strip was provided by the police to allow authorities to account for residents in a building.