The bodies of a man and a woman were discovered after police broke into the property in Cann Bridge Street in Higher Walton at around 1:40pm.
Officers said the deaths were being treated as "suspicious."
A police spokesman said: "We were called at 1.40pm today to a concern for safety of the occupants of the property in Cann Bridge Street, Higher Walton.
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"Officers forced entry and sadly found a man and a woman decease inside.
"Their deaths are being treated as suspicious and a crime scene is currently in place."
It is understood officers have made an arrest, but no details have so far been released.
Police patrols in the area have been stepped up to reassure the public.
An appeal for information about the incident has been made. Anyone with information should call 101, quoting log 0841 of November 20, 2021.