The former British agent known as Kevin Fulton who was arrested in London by PSNI officers earlier this week has been released without charge.
Kevin Fulton was a British agent in the IRA
He had been brought back to NI to be questioned about the murders of Eoin Morley and Ranger Cyril Smith.
Ranger Smith died in a bomb blast in 1990 while trying to rescue a man who had been forced to drive a car bomb into a checkpoint near Newry.
Eoin Morley, 23, was shot dead in the Derrybeg area of Newry in 1990.
The killing came amid tensions between the IRA and the Irish People's Liberation Organisation, a splinter republican paramilitary faction.