An unassembled explosive device was found in an abandoned suitcase inside the Port Authority Bus Terminal, police sources said Thursday.

Port Authority cops called the NYPD bomb squad after finding the luggage around 8 p.m. on the first floor near Deli Plus.

They looked inside the case and found “a fuse assembly and black gunpowder, the items were not assembled and non-operational,” an NYPD spokesman said.

A man named Arsenio Mason, 39, was arrested by Port Authority cops when he returned to the terminal and asked about the suitcase.

Mason appears to match the description of a man seen on surveillance planting the suitcase, police sources said.