Half a century after Seamus Maguire was abducted and became one of the “disappeared” of Northern Ireland’s Troubles, a search for his remains has begun in two acres of County Antrim farmland.

A team of forensic experts started the dig on Tuesday in the Derryclone townland where republican paramilitaries are believed to have killed and secretly buried the 29-year-old in 1976.

The Independent Commission for the Location of Victims’ Remains (ICLVR), an agency tasked with finding bodies of the disappeared, said “credible evidence” indicated Maguire was buried in the area.

It is not clear if the Provisional Irish Republican Army or another republican group killed Maguire, who was from Aghagallon, near Lurgan. Originally it was believed that he vanished in 1973 or 1974 but it was later determined that he may have spent time in Manchester before returning to Northern Ireland, and being murdered, in 1976.

The team will search until it finds what it seeks or is satisfied that Maguire is not there, said Eamonn Henry, the lead investigator. “I’m not going to put a specific timeframe on the search.”

In a statement Maguire’s family called him a “much loved eldest brother” who had been missed for more than 50 years. They expressed hope his body would be recovered so he could be buried in St Patrick’s graveyard in Aghagallon with his parents, May and Patrick. “Our mum looked for Seamus right up until the day that she died.” The family thanked the commission and appealed for privacy.

Of the approximately 3,600 people killed in the Troubles, the fate of the 17 officially designated “disappeared” proved especially harrowing for families. Some for a time nurtured false hope that their loved ones were alive before agonising over when, where and how they were killed. The absence of a body compounded grief.

The commission, which was established by the 1998 Good Friday agreement, has found 13 of the 17 bodies, leaving four that are still missing: Maguire, Joe Lynskey, Robert Nairac and Columba McVeigh.

Last December it combed boggy soil in County Monaghan across the Irish border – without success – for the remains of McVeigh, who was 19 when the IRA abducted and shot him in 1975.

The Antrim farmland that may contain Maguire’s remains is more stable but each search throws up its own challenges, said Henry. The decision to search a site did not mean the commission had all the information it needed, he said.

“If there is anyone who has any information on this case, please get it to us. All information is treated in the strictest confidence and our sole purpose is to return the remains of a loved one to their family for a Christian burial.”

Hilary Benn, the Northern Ireland secretary, thanked the commission for its efforts to ease the “long suffering” of the families of the disappeared.

“My thoughts are first and foremost with the Maguire family, who have endured so many years of anguish since the abduction and disappearance of Seamus. As well as the Maguire family, the families of Columba McVeigh, Joseph Lynskey and Robert Nairac still await the return of their loved ones’ remains.” Benn urged anyone with information to come forward, saying it would be treated in the strictest confidence.