Police in New York City have arrested a couple after finding a substance used to make explosives as well as bomb-making manuals in their apartment.

U.S. authorities say the 31-year-old man, Aaron Greene, and his 27-year-old girlfriend, Morgan Gliedman, are being charged with possessing weapons.

They say detectives discovered seven grams of HMTD, an explosive commonly used in homemade bombs. Police also found numerous written items containing instructions on manufacturing explosives, including a cover page entitled The Terrorist Encyclopedia.

Greene appeared in court Sunday and is being held without bail, while Gliedman is still awaiting an initial court appearance. She is the daughter of a prominent Manhattan doctor.