Suspected illegal immigrants were found living in a rat-infested house.
Eight men and women were held on suspicion of being in the country illegally after officers from Wealdstone and Marlborough Safer Neighbourhoods Team executed a search warrant at an address in Byron Road, Wealdstone on Monday.
Police, Harrow Council and immigration officers had received information that the house was overcrowded.
Officers found 13 people living in the three-bedroom house, where they were sleeping on mattresses on the floors.
The house was infested with cockroaches and had signs of rat droppings in every room.
Harrow Council housing officers are questioning the landlord, who had not registered his property for letting out.
Cllr Varsha Parmar, who is responsible for environment, crime and community safety, said: “We are going to work with police on protecting tenants and ensuring that the crush on housing does not become a licence to rip off the vulnerable.”