Lancashire Police reported that the bodies of a man and a woman were discovered at a house on Hardman Street in Blackburn at around 08:20 BST. Both individuals were pronounced dead at the scene.
A man in his 40s has been arrested on suspicion of murder. Police have assigned a dedicated team of officers to the case, who are conducting CCTV, house-to-house, and forensic inquiries. The crime scene is expected to remain in place for several days.
Detectives are working to establish a motive for the deaths, though police have stated they do not believe there is a wider threat to the community. Officers have appealed for anyone with information to contact them.