The U.S. Secret Service on Monday announced the discovery of a secret communications network of more than 100,000 SIM cards and 300 servers capable of carrying out “nefarious” attacks as world leaders began gathering in New York for the annual U.N. General Assembly.

The devices, which they said were found within 35 miles of the U.N., had the potential to shut down the entire cell phone network in New York City, Matt McCool, the special agent in charge of the New York field office, claimed in a videotaped announcement.

The agency is investigating whether the network — which McCool said is tied to foreign actors and “individuals known to law enforcement” — was intended to disrupt communications of government and emergency personnel during the conference.  

Investigators believe the devices were “used to conduct multiple telecommunications-related threats directed towards senior U.S. government officials, which represented an imminent threat to the agency’s protective operations,” an agency press release said.

The network, which has been dismantled, also could be used for encrypted communications between threat actors, according to the press release.

“This network had the potential to disable cell phone towers and essentially shut down the cellular network in New York City,” McCool said.

The Secret Service is investigating who placed what the agency described as highly sophisticated equipment and is now analyzing 100,000 cell phones worth of data, he said. 

The agency made the discovery public in an effort to protect critical infrastructure, McCool added.