MADISON, Wis. (AP) — The man accused of firebombing a prominent Wisconsin anti-abortion group’s office has pleaded not guilty.

Investigators believe Hridindu Roychowdhury, of Madison, threw two Molotov cocktails into the Madison office of Wisconsin Family Action last May. He entered a not guilty plea Tuesday to one count of attempting to cause damage by means of fire or an explosive. He also waived his right to appear in court for an arraignment once he is returned to Wisconsin.

One of the firebombs thrown into the anti-abortion group’s office failed to ignite; the other set a bookcase on fire. No one was in the office at the time. The message “If abortions aren’t safe then you aren’t either” was found spray-painted on the building.

Police arrested Roychowdhury in a Boston airport last month after investigators matched his DNA to samples from the crime scene. He had a one-way ticket to Guatemala, according to the U.S. attorney’s office.

Myra Longfield, a spokesperson for the U.S. attorney’s office in Madison, said Thursday that Roychowdhury is being held in federal custody but has not yet been returned to Wisconsin. A date has not been set for his initial appearance in court.