Detectives say a woman whose body was found at a flat in west Belfast on October 6, may have died more than two years ago.
Detective Chief Inspector Alan Dickson said: "Authorities were alerted on Friday after concerns were raised about the welfare of 68 year old Marie Conlon.
"Officers forced entry to her Larkspur Rise home and discovered her deceased in bed. It was apparent that she had lain undiscovered for some time.
"A post mortem examination was carried out and the results suggest that the death may have been suspicious. Further testing is due to take place."
Detectives investigating the circumstances of the death have established that the last known sighting of Ms Conlon was in January 2015.
"It is our belief, supported by the medical evidence, that her death may have occurred at around this time," added Detective Chief Inspector Alan Dickson.
"We have launched a murder investigation and a 23 year old man has been arrested on suspicion of a number of offences including murder.
"He was detained in the west Belfast area yesterday and remains in custody at present. Anyone who believes they may have information that could assist the police investigation is asked to call police on 101."