Federal prosecutors say a New Hampshire man accused of phoning in bomb threats to Harvard University and demanding a large amount of Bitcoin was not acting alone.

The comments came Friday during the first court appearance for William Giordani, who was released on conditions, court records say. He’s due in court again later this month.

Giordani was arrested Tuesday on charges of conspiracy and aiding and abetting extortionate threats.

“We don’t believe that Mr. Giordani acted alone,” WCVB.com reported federal prosecutor John McNeil said in court on Friday. “We will be looking for other individuals.”

On April 13 the Harvard University police department received six calls regarding bombs and demand for payment. The caller gave a location and a description of a device, which police found and destroyed. The area was evacuated, but no other devices were found.

Police allege Giordani was seen on camera picking up some of the items at a home goods store and on surveillance video near where the device was found. Giordani later told police that “all he did” was respond to a Craigslist ad and “just put some fireworks in a safe and put them at Harvard,” a court affidavit said.

But police say Giordani placed a Craigslist ad posing as a parent of a Harvard student saying they needed someone to drop off supplies for their son.

Giordani’s defense attorney Jane Peachy said Friday that Giordani did not write the Craigslist ad.