Media reports suggest the Manchester Arena bomber was renting a short-let property in the centre of the city before he committed the atrocity.
A number of newspapers and online news outlets say that armed officers raded an apartment close to Manchester Piccadilly station in connection with the blast.
A statement from Greater Manchester Police says: "Officers have ... carried out a search at an address in Manchester city centre as part of the investigation into the horrific incident at Manchester Arena. That search is ongoing."
The bomber, Salman Abedi, blew himself up at the Arena, killing 22 people including himself and injuring over 60 others.
Short let properties can be let with almost none of the checks expected of a letting agent or private landlord who lets a property for longer periods.