Officers found the bodies of a man and a woman inside the property in Livingston late on Sunday night.
A spokeswoman for Police Scotland said: “Officers were made aware about 11.40pm on 26 December, of a report of a sudden death in the Raeburn Rigg area of Livingston.
“A man and a woman were found dead inside a property.”
She confirmed a 19-year-old man had been arrested in connection with the incident.
She added that inquiries were ongoing to establish the full circumstances of what happened but the investigation was at an early stage.
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