The PSNI say the suspect has been freed pending a report to the Public Prosecution Service.
The naked body of the Derry republican – known to his friends as ‘Shorty’ – was found on the shores of Lough Neagh near Toomebridge, in January 2008.
It was recovered six weeks after the family of the Derry man reported the 53-year-old missing.
A pathologist who carried out a post mortem examination on his remains said a possible cause of death was drowning and “there must be considerable suspicion around his death.”
The Office of the Police Ombudsman Dr Michael Maguire subsequently carried a probe into police conduct over his disappearance.
Dr Maguire recommended that 10 police officers be disciplined.
At the time he went missing Mr Hampson was wanted for questioning in connection with a double abduction in Co Westmeath and a shooting in Derry in 2007.
A brother-in-law of the late Sinn Féin leader Martin McGuinness, Marvin Canning, was charged in connection with the episode but the prosecution was later dropped.