Alison McDonagh, 49, and Stephen McParland, 54, were arrested in the Newry area on Thursday afternoon.
McDonagh was imprisoned for a murder committed in 2004; McParland received his conviction for a killing in 1997.
They had been last seen at Lanyon Place train station in Belfast at about 13:45 GMT on Saturday.
According to the Department of Justice, McDonagh was on a pre-release scheme and McParland was on pre-release testing.
McDonagh, then known as Alison Michelle Martin, was convicted in July 2006 for the murder of 47-year-old George McDowell.
Mr McDowell was stabbed to death in a flat in the Rathcoole estate in Newtownabbey in July 2004.
McParland was convicted in 1998 of the murder of Gary Alexander McKimm in an alleyway off the Cregagh Road in east Belfast in January the previous year.
His trial was told he had punched, kicked and stamped on Mr McKimm, who he had been drinking with, in a row over £20 owed by one of them to the other.