A 14-hour joint operation by officers from the police and Central Narcotics Bureau ended with 20 people arrested on Tuesday.
Checks were conducted at public housing estates in Sembawang, Yishun, Ang Mo Kio, Hougang and Serangoon.
During the operation, a male subject was arrested for buying illegal 4D in the vicinity of Buangkok Crescent. A mobile phone containing entries related to illegal public lottery was seized.
A total of 19 people were also arrested for drug-related offences.
Investigations against those arrested are ongoing.