The bodies of a man and woman were found at the property by police in Cann Bridge Street, Higher Walton at 1.40pm on Saturday.
Their deaths are being treated as suspicious and a scene is currently in place.
A 35-year-old local man has been arrested on suspicion of their murders.
Lancashire Police confirmed the family of the victims have been made aware of the latest development and are being supported by specially-trained officers.
Anyone with information should call 101, quoting log 0841 of November 20, 2021.