Of them, three had minor bruises, while two, Rehman (26) and Maran (31), were treated at a private hospital and are said to be stable.
The two were working on the second floor of the three-storey commercial complex when a portion of the staircase collapsed on them, Mico Layout police said. The three others were near the staircase when it collapsed.
The police suspect the collapse was because of faulty centring that could not support the weight of the structure. They have registered a case of negligence against the owner of the building Rahim, who has been picked up for questioning.
The incident comes close on the heels of the building collapse in Kengeri last week, which killed three labourers and injured 11 others.