The FBI said Tuesday that it found "explosive residue" in a Pennsylvania storage unit believed to be connected to an "ISIS-inspired terrorism" incident near New York Mayor Zohran Mamdani's residence over the weekend.
The FBIsaid on Xthat it found the explosives and that authorities "conducted a controlled detonation." The explosives are "believed to be connected" to Saturday's incident, in which improvisedexplosive devices were thrownoutside Gracie Mansion during protests.
Two Pennsylvania teenagers — Ibrahim Kayumi, 19, and Emir Balat, 18 — face federal charges in connection with the incident.
None of the devices were detonated, and nobody was injured.
A senior law enforcement official briefed on the investigation said several components and chemicals were removed from the Pennsylvania storage facility. The official added that local police detonated some of the components out of precaution late Monday.
NBC News has obtained surveillance video allegedly showing Balat buying a fireworks fuse at a store in Pennsylvania on March 2, five days before the incident.
Phantom Fireworks said the video, which it shared with NBC News, shows 18-year-old Balat drive to its Penndel store around 12:40 p.m. and walk in.
The company said the video shows Balat registering his identification with an employee — something the company requires all customers to do — and purchasing a single 20-foot roll of green safety fuse with cash.
Phantom Fireworks Executive Vice President Alan Zoldan said that after the attempted bombing outside the mayor's residence, the company searched its records for both suspects' names.
Balat was a match, which led the company to video of his roughly 10-minute store visit, Zoldan said.
Zoldan showed NBC News a copy of the subpoena he says federal prosecutors sent Phantom Fireworks.
The FBI declined to comment.
The criminal complaint against Balat and Kayumi, filed in U.S. District Court for the Southern District of New York, alleges that they made statements about the Islamic State terrorist group before and after their arrest.
Body camera video from the New York City officers who arrested Kayumi shows him responding "ISIS" to someone in the crowd asking why he had done it, according to the complaint.
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Federal prosecutors said the pair hoped to inflict more carnage than theBoston Marathon bombing, whichkilled three people and injured more than 260 others in 2013.
A person who answered a phone number associated with Balat's father, Selahattin Balat, told NBC News that the Balat family would not comment on the case.
Kayumi and Balat were being held Tuesday pending an application for bail. They face several charges, including unlawfully possessing and using a "weapon of mass destruction," transporting explosives and attempting to aid a "designated foreign terrorist organization," according to the federal complaint.
At a court hearing Monday, attorneys for the teens requested protective custody for their clients at the Metropolitan Detention Center in Brooklyn.
"This is a publicly declared terror trial, this is the city of New York, he's 18, and he's exposed to the general population of what is called a hellhole, and we want to keep him protected," Mehdi Essmidi, Balat's attorney, told NBC News on Monday.
An attorney for Kayumi did not immediately reply to a request for comment. Both suspects are from Bucks County in southeastern Pennsylvania, with Balat residing in Langhorne and Kayumi in Newtown, according to authorities.
While it was not immediately clear how Kayumi and Balat know each other, a source familiar with the matter told NBC News that they drove from Pennsylvania to New York City in a car borrowed from an associate.
That associate did not know what the two men are alleged to have been up to in allowing them to borrow the vehicle, the source said.
Separately, questions are being asked about whether unexplained explosion sounds in Pennsylvania that occurred in January can be attributed to the suspects. The explosions occurred in a town next to where one of the suspects lived, NBC Philadelphia reported.
At a news conference Monday with police, Mamdani said he and his wife, Rama Duwaji, were at a museum in Brooklyn when the explosives were thrown, and he condemned the incident.
Mamdani, the city's first Muslim mayor, also castigated the original event's taking place outside his official residence, calling it a "vile protest rooted in white supremacy."
The anti-Islam demonstration, called "Stop the Islamic Takeover of New York City, Stop New York City Public Muslim Prayer," was led by conservative provocateur Jake Lang, 30. It drew roughly two dozen protesters and more than 120 counterprotesters, according to police.
Lang declined a request to be interviewed.
Lang, who was pardoned for charges tied to the Jan. 6, 2021, attack on the U.S. Capitol, held a similar rally in Minneapolis in January. The anti-immigration protest was held in the days after a federal immigration officershot and killed Renee Good.