Major Crime Squad detectives have charged a 36-year-old Midland man with the murder of his defacto partner, found fatally injured in their Midland unit on Wednesday.

Detective Mark Fyfe said a man they knew, who visited their Cooper Street home that afternoon, called an ambulance before paramedics took the woman, 42, to the local St John of God hospital, but she was declared dead upon arrival.

Police have made an arrest in relation to a murder in Midland.

While a pathologist had "noted certain injuries to her body" which he said were "around her throat," her cause of death has not been confirmed.

The accused was refused bail and will appear at Midland Magistrates Court on Friday.