Two women being questioned about the murder of the former UDA east Belfast commander, Jim Gray, were released without charge last night.
Four men arrested in connection with the investigation are still being detained.
Gray, who was 47, was shot dead on Tuesday night outside his father's house on the Clarawood estate.
Police say the involvement of the UDA in the killing is a major line of inquiry.
Gray was expelled from the loyalist paramilitary group last March.