NEW YORK (AP) — New York City’s police commissioner said Monday that authorities are investigating whether men who brought improvised explosive devices to a protest outside New York City’s mayoral residence were inspired by ISIS.

The devices, which did not explode, were hurled during raucous counterprotests Saturday near Gracie Mansion during a “Stop the Islamic Takeover of New York City” event led by the far right activist Jake Lang. Police Commissioner Jessica Tisch said the explosives could have caused serious injury or death.

Two people are in custody for their alleged roles in the confrontation but they have not been charged, Tisch said during a news conference. Police are working with federal prosecutors and the FBI, which has assigned agents with the bureau’s Joint Terrorism Task Force to the investigation.

“I can confirm this morning that this is being investigated as an act of ISIS-inspired terrorism,” Tisch said.

The two have not been charged. Tisch said police were working with federal prosecutors and the FBI on the case. The FBI said agents with the bureau’s Joint Terrorism Task Force were participating in the investigation. She said investigators have found no apparent link to Iran or the war.

“At this time, we do not have any information that connects this investigation to what’s going on overseas in Iran,” Tisch said.

The sparsely attended protest Saturday drew a far larger group of counterdemonstrators, including one person who police say tossed a smoking object containing nuts, bolts, screws and a “hobby fuse” into the crowd.

The device extinguished itself steps from police officers, Tisch noted. The same person who threw it then dropped a second device that did not appear to ignite, the commissioner said.

On Saturday, authorities said they “identified a suspicious device in a vehicle on East End Avenue between 81st Street and 82nd Street.” Several streets were closed and nearby buildings were evacuated. Around 7 p.m., police used a flatbed truck to remove a Honda Civic and the streets were reopened.

Lang was charged with assaulting an officer with a baseball bat, civil disorder and other crimes for his part in the Jan. 6 insurrection but was freed from prison as part of President Donald Trump’s sweeping act of clemency. Lang recently announced that he is running for U.S. Senate in Florida.

Earlier this year, he organized a rally in Minneapolis in support of Trump’s immigration crackdown, drawing an angry crowd of counterprotesters that quickly chased him away