A new discovery has emerged about the deaths of 57 Irish railroad workers at Duffy’s Cut in Chester County in the early 1830s, writes Genevieve Glatsky for the Philadelphia Inquirer.

The young Irish immigrants came to the United States to work on the old Philadelphia & Columbia line in Malvern. However, all of the workers were dead within a few months of their arrival, with official reports listing the cause of death as cholera.

For decades, the mysterious circumstances surrounding the event made the Irish-American community suspect foul play. Those suspicions were validated 15 years ago, when twin brothers William and Frank Watson discovered family documents that contradicted the original report. This prompted the brothers to start searching for answers.

Excavations from several years ago found the remains of seven people who had died violently by bullets and axes. William believes they were murdered by a vigilante group out of a fear of the disease and prejudice against the Irish.

This belief may now have been further validated, as the Watsons’ discovery by ground-penetrating radar shows that there could be another mass grave there.

Read more about the new discovery in the Philadelphia Inquirer here.