Authorities in Singapore have arrested 45 Indians for alleged immigration offenses after a raid on an apartment.

Singapore Immigration and Checkpoints Authority stormed the three-storey apartment in Geylang Tuesday night and found many inmates sleeping on rooftop and other parts of the building.

"Many of the offenders were sleeping on clothes placed on the floor with no shelter over their heads. There were some rooms on the same level which were also occupied by them," ICA said in a statement. "Those found in these dirty and messy rooms were also sleeping on the floor."

Preliminary investigation showed that the offenders -- all males ranging from 21 and 54 years old -- were daily wage workers earning about US $25 per day.

Under Singapore's Immigration Act, penalties for overstaying or illegal entry are a jail term of up to six months plus a minimum of three strokes of the cane, Bernama news agency said in a report.