The police have arrested 40 migrants caught living in Malta illegally, the Home Affairs ministry said following early-morning raids in Marsa, Hamrun and Attard.
In a statement, the ministry said the police carried out the raids together with detention officers and environmental health officers.
The ministry said inspections were carried out on the street, on bus stops as well as in several derelict buildings.
The police will also be investigating the owners of the buildings housing the migrants as part of ongoing efforts to promote lawful behaviour, the ministry said.
"In the coming weeks we will strengthen our efforts and there will be a number of similar operations around Malta and Gozo.
"This is so that the authorities continue to fight the issue of illegal immigration as part of a strategy that is built on prevention, returns and relocations," Home Affairs Minister Byron Camilleri said.