OAKLAND — In an unusual set of allegations for Northern California’s federal court, a man is being held in the Bay Area on charges that he conspired to smuggle Irish nationals into the United States by sea.

William O’Reilly Jr., a 23-year-old roofer living in Charleston, Massachusetts, has been identified by prosecutors as the leader of “an alien smuggling enterprise spanning the United States and Canada.” He was arrested Monday in Northern California and is being jailed in the Bay Area after prosecutors convinced a judge that O’Reilly is a potential flight risk, according to court records.

The charges, filed March 18 in New York federal court, accuse O’Reilly of working with others to sneak people into the United States. One of the other suspected co-conspirators, who is referred to in court records by an alias, reportedly told federal investigators that O’Reilly and the unnamed person would “prepare a boat to smuggle aliens from Canada into the United States.”

The alleged co-conspirator later told authorities that he believed some of the “Irish” brought into the United States were involved in criminal activity, and that O’Reilly — who was born in County Clark, Ireland — would be paid in cash for his work. The unnamed co-conspirator gave up this information after being arrested and charged with alien smuggling last November, according to court records.

O’Reilly remains in the Bay Area for now, pending extradition to New York. He has not yet had a chance to respond to the charges in court or enter a plea.