DETECTIVES are probing links between the murder of a former garda and that of a dog breeder who disappeared two years ago.
A man has been arrested by officers investigating the disappearance of Gerry Daly, who was 42 when he went missing from his home in Co Cavan in June 2011.
His neighbour, former garda John Kerins, who was shot in the head last November, was previously questioned over the whereabouts of the missing man.
After upgrading the investigation into the man's disappearance to murder, det- ectives are now understood to be probing links to the killing of Mr Kerins, who was found dead on the couch in his home.
An extensive investigation failed to find evidence suggesting Mr Kerins was linked to Mr Daly's disappearance, but officers believe both men were victims of the same crime gang.
A garda spokesman confirmed that a 53-year-old man was arrested and can be questioned for up to 24 hours in Carrickmacross garda station.
It is understood detectives made a significant breakthrough in the Daly case and have uncovered "evidence that a murder took place", according to security sources.
It is unknown if gardai have located the body of the missing man.
Mr Daly was last seen alive at his home in the townland of Cornaveagh, near Bailieborough, on June 26, 2011.
There was no sign of a struggle or a disturbance at his home, and the only things known to be missing were his mobile phone and the keys to his van.
Gardai always suspected that Mr Daly, originally from Knockmore Grove in Tallaght, Dublin, had been murdered and buried in a secret location.
He and Mr Kerins were said to have been planning to go into business together breeding guard dogs, before Mr Daly's disappearance. Mr Kerins, who was 49 and had been medically discharged from the force several years earlier, was arrested and questioned by gardai when his neighbour went missing.
Mr Daly was described as 5ft 10in, of broad build, with dark hair and blue eyes.
His family have made several public appeals since his disappearance urging anyone, even with the smallest piece of information, to come forward and tell gardai.
Investigations into his whereabouts included searches and inquiries in the Bailieborough area as well as the border region and in England, Jersey and Malta.
Gardai have also been working closely with the PSNI, Interpol and Europol and detectives from the National Bureau of Criminal Investigation to try to solve the mystery of his disappearance.
In January, a convicted Real IRA bomber made a complaint to Garda Commissioner Martin Callinan claiming that he was being "harassed" by officers investigating the Kerins murder.
John Connolly, who was released from Maghaberry Prison in 2007 after serving half of a 14-year prison sentence, was the leader of the RIRA prisoners while inside.
In 2000, he was caught along with three other men in possession of a mortar at the Teemore crossroads on the main Enniskillen to Cavan Road. He was also convicted of RIRA membership.
Through his solicitor, Connolly made a complaint to Mr Callinan about what he claims is harassment by detectives who searched the Co Cavan home of his girlfriend and tried to question him about the murder without a warrant.
Connolly has denied any involvement in the Kerins killing.