Three controlled detonations were heard after FBI agents searched the Public Storage facility on South Flowers Mill Road in Bucks County and blew up the containers.
The facility is not far from where the FBI executed search warrants at the homes of the 18-year-old Emir Balat and 19-year-old Ibrahim Kayumi.
Prosecutors, police and FBI officials say Balat and Kayumi drove to New York City on Saturday and joined a throng of counter-protesters at a small, anti-Muslim rally outside the mayor's residence, organized by the far-right Christian nationalist Jake Lang.
The suspects are accused of throwing and igniting two objects, one of which was confirmed to be an IED during the protest.
The two men who allegedly carried the devices are charged in a five-count federal complaint with attempting to provide support to ISIS, use of a weapon of mass destruction and other charges.
As they were walked out of a police precinct on Monday morning, Balat apparently made a hand gesture that shows support for ISIS.
Police say both suspects claimed they were inspired by ISIS.
In court papers, Kayumi allegedly told police "...that he was affiliated with ISIS; watched ISIS propaganda on his phone; and was partly inspired to carry out his actions that day by ISIS."
Balat allegedly claimed "...that they wanted to carry out an attack bigger than the Boston Marathon bombing, which Balat noted caused only 'three deaths.'"
A federal magistrate ordered both men held without bail following their brief appearance. The two men appeared in white Tyvek suits, seated at the same defense table, separated by their attorneys.
The young men were shackled and said nothing other than answering a basic question or two. They did not enter a plea.
Meanwhile on Tuesday afternoon, with tensions still high following the events over the weekend, police sealed off East End Avenue outside Gracie Mansion. This time, after a parks worker spotted something suspicious along the East River promenade in Carl Schurz Park.
After nearly three hours, the lockdown would be lifted after the object was determined to be a jar filled with harmless liquid.
Mayor Zohran Mamdani thanked the NYPD for their quick response.
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