Some 175 years ago this month, a group of young, single men left Tyrone in search of a better life in America. Leaving behind a country in the grip of famine and poverty, the men migrated across the Atlantic where they took up work in a Pennsylvanian town on America's eastern seaboard, labouring for the country's emerging railroad industry.

With others from Derry and Donegal, they were part of a group of 57 Irishmen who, like so many others in the mid-19th century, left home in search of a new life. Within six weeks of arriving, however, all 57 men were dead.

For decades their tragic story became forgotten and ultimately lost in the passage of time, until a chance discovery by two American brothers three years ago reopened one of Irish history's great unsolved mysteries.

Now, almost two centuries on, as reported in Monday's Tyrone Herald, a team of experts believe they are just days from uncovering the truth about the men's deaths.

If successful, they could cast new light on a tragic episode in local history and add a closing chapter to a clandestine story which lay hidden in a dusty American filing cabinet for almost 100 years.

Rural Tyrone in the early 19th century was a harsh, unforgiving society. In 1831 a famine had hit western Ireland, coinciding with the emigration of hundreds of young Irishmen from the province in search of a better life in the New World.

The 57 men are known to have arrived in Philadelphia on June 23 1832 after crossing the Atlantic on board a ship, the "John Stamp", which departed from Derry on a one-way journey to hope and apparent prosperity.

There they were hired by an Irish contractor called Philip Duffy, who had emigrated from Tipperary a generation beforehand and become involved in the railroad industry, one of the great industrial innovations of the period.

The men were commissioned by Duffy to build a one-mile stretch of railroad, the first of its kind in Pennsylvania and one of the earliest in the United States, during the construction of the Philadelphia and Columbia Railroad.

Their work would have been painstaking and arduous. They were tasked with clearing and straightening a portion of hilly terrain for the railroad tracks on a section of line that became known as Duffy's Cut.

By August 1832, just six weeks after their arrival in the States, all 57 men were dead, the victims of an apparent cholera epidemic. Their bodies were taken and secretly buried in an unmarked mass grave near the neighbouring town of Malvern.

Their tragic story would have been forgotten but for a chance discovery by two American brothers, Dr Bill Watson and his brother Frank, of an old file stashed among their grandfather's papers back in 2004.

Since then the men, working alongside two other experts, have embarked on an extensive research operation stretching across the Atlantic aimed at piecing together the truth about the men's deaths.

Along the way they have uncovered evidence of violence, murder and secret cover-ups. It is an astonishing story of exploitation, bigotry and neglect, the dark side of the American dream.

Five years ago Dr Watson, a professor of history at Immaculata University in Philadelphia, uncovered papers that once belonged to his grandfather. During the mid-19th century he had served as assistant to the president of the Pennsylvanian Railroad, Martin Clement.

On the file were instructions stating that the enclosed papers should never be removed from the office. There were also references to other documents which are missing, believed destroyed, detailing the events of that summer.

Experts now believe the missing files were deliberately removed as part of a cover-up of the men's deaths which, they claim, may hide a more sinister secret.

"These men were not liked, these men were not wanted," states Dr Watson. "And the fact that there was a 100% casualty rate suggests there was more than cholera at work here. It suggests there might have been foul play.

"Duffy's Cut is a unique historical site in that the entire immigrant work gang perished from an epidemic disease that, even under the most horrendous conditions in 1832, should have claimed around 50% to 60% of its victims."

According to Professor John Ahtes, an Irish history expert at Immaculata University, contemporary documents have indicated widespread ethnic and religious prejudices at the heart of American society at the time.

"Duffy's Cut is the dark side of the Irish immigrant experience in the early 19th century in America," he states. "There was rising ethnic and religious prejudice and the association of the Irish in bringing the global pandemic of Asiatic cholera to North America.

"These men counted for little or nothing and were dumped in a ditch and forgotten as though they were work animals. It's a grim story but representative of the time, and it has struck a chord here with the Irish-American community."

Fascinated by the events of summer 1832 the men, in conjunction with Earl Schandelmeier, a history assistant at the university, undertook a massive project aimed at recovering the men's remains.

Since 2004, they have been involved in major archaeological and research work to discover who the men were and their final resting place, ultimately in the hope of providing them with a proper burial in consecrated ground.

They are nearing a fascinating conclusion, with last week's find providing a major breakthrough in the search for the men's bodies.

The discovery of the burial site was announced on Wednesday after an expert in geo-physics, Tim Bechtel from the University of Pennsylvania, was brought in to scan the surrounding area using subsurface imaging technology.

Based on the scan a computer image of an "anomaly" that signifies the location of the mass grave has been produced, and excavation work on the site will begin later this week.

"This is an enormously important breakthrough," added Dr Watson. "For the first time in 175 years we have got an image of these poor men in their final resting place.

"We have all the necessary permits and information to exhume them from this ignominious grave and place them in a proper grave in consecrated ground."

The Watsons plan to have the men reinterred at the West Laurel Hill Cemetery in Philadelphia. The cemetery has donated the plots and the coroner has made the area where the men are buried a crime scene so that the bodies can be exhumed.

"We should know within days if not sooner what exactly is under this area and once we find remains they will go to the local coroner. The area has been declared a crime scene because there is the possibility that violence was used and that some of these men were murdered.

"We should be able to discover the truth from the remains and we are hopeful that we can provide a firm conclusion to this story in the coming days."