It follows the discovery of a man’s body was found in a car in Lisburn.
The victim was discovered in the Limehurst Way area of Lisburn on Monday afternoon.
A post-mortem examination is to be carried to give an exact cause of death which is being treated by MIT detectives as suspicious.
The man has been arrested on suspicion of murder.
Police do not believe there is any paramilitary involvement in the incident.
He has been taken to Musgrave PSNI station for questioning.
Detective Chief Inspector Peter Montgomery of the MIT said: “Police are investigating the circumstances surrounding the death of a man whose body was discovered in a car in the Limehurst Way area of Lisburn this afternoon, Monday 26 September.
“Police received the report shortly after 4.20 pm.
“We would appeal to anybody who may have information in relation to this suspicious death or who was in the area of Limehurst Way today between 9 am and 5 pm to contact detectives at the incident room in Lisburn on 101.”