Detectives were quizzing a 35-year-old man after the bodies of two people were found in a house.
The un-named suspect was being held in custody on Sunday after the bodies of a man and woman were found in a property in a Lancashire village.
Police were called at 1.40pm on Saturday to the house at Cann Bridge Street, Higher Walton, between Preston and Blackburn after a concern for welfare report.
Officers made a forced entry and found a man and a woman dead inside the property.
Their deaths are being treated as suspicious and a scene is currently in place.
Police said: "The family of the victims have been made aware of the latest development and are being supported by specially-trained officers.
"Our thoughts remain with them at this time."
A dedicated team of detectives have been assigned to the case and enquiries are ongoing.
Reassurance patrols have been stepped up in the area as a precaution.
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