Less than two months after 57 Irish immigrants were hired to lay railroad track in Pennsylvania in 1832, all were dead. Were they victims of a cholera epidemic or something much darker?

Less than two months after 57 Irish immigrants were hired to lay railroad track in Pennsylvania in 1832, all were dead. Were they victims of a cholera epidemic or something much darker?
They laid his bones in a bed of Bubble Wrap, with a care beyond what is normally given to fragile things.
See stills and behind the scene images of Secrets of the Dead: Death on the Railroad
Less than two months after 57 Irish immigrants were hired to lay railroad track in Pennsylvania in 1832, all were dead. Were they victims of a cholera epidemic or something much darker?