The man who was arrested after police found explosive materials and terrorist literature in his Greenwich Village apartment, also allegedly had plans to "blow up" the iconic Washington Arch, sources say.

The New York Times reports several sources have told investigators they observed 31-year-old Aaron Greene "sprinkling a white powder on the sidewalk inside Washington Square Park and then striking it with a rock, triggering an explosion."

NYPYD spokesman Paul Browne said authorities believe the white powder was most likely hexamethylene triperoxide diamine or HMTD.

7 grams of the dangerous, highly explosive powder were uncovered inside the home Greene and his girlfriend Morgan Gliedman shared in the Manhattan neighborhood.

27-year-old Gliedman was also arrested. She was nine months pregnant at the time of her arrest and gave birth to a baby girl while under police custody.

Gliedman has since posted bail and was ordered to attend 30 days of inpatient treatment at a rehabilitation center.

The couple have a history of criminal activity including drugs and suspected robbery.

On Wednesday, Browne said Greene was the "focus of the investigation."

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