A massive illegal electronic device network capable of crippling cell towers and jamming 911 calls across New York City was uncovered by the Secret Service — just as world leaders prepared to descend on Manhattan for the UN General Assembly, officials said Tuesday.

Investigators discovered the trove of devices — including more than 300 co-located SIM servers and 100,000 SIM cards – at multiple locations within 35 miles of the United Nations.

“The potential for disruption to our country’s telecommunications posed by this network of devices cannot be overstated,” Secret Service Director Sean Curran said.

Officials warned the devices had the capability of carrying out a wide-range of telecommunications attacks — including spamming networks with up to 30 million text messages a minute — that could have had “catastrophic” consequences for the city.

Investigators also believe the networks could be tied to making spam threats to US officials, and had communicated with people in foreign countries.

The feds are investigating whether the devices have ties to a foreign government. 

“It can take down cell towers, so then no longer can people communicate, right? …. You can’t text message, you can’t use your cell phone. And if you coupled that with some sort of other event associated with UNGA, you know, use your imagination there, it could be catastrophic to the city,” Matt McCool, the special agent in charge of the Secret Service’s New York field office, said.

“Given the timing, location and proximity and potential for significant disruptions to the New York telecoms system, we moved quickly to disrupt this network.”

It wasn’t immediately clear exactly when the cache of hidden devices was seized, nor their precise purpose.

However, law enforcement sources said that similar operations had been uncovered in California and the Midwest in recent weeks. 

The sources said that the investigation is ongoing but they appeared to be linked to spam calls, but also could have a more benign purpose like acting as a proxy for international calling cards. 

Some cybersecurity experts also warned about the potential for dangerous security threats from the devices.

“My instinct is this is espionage,” Anthony Ferrante, global head of consulting firm FTI’s cybersecurity practice, told the New York Times. 

He noted the setup had all the hallmarks of a costly operation, which could be used for eavesdropping as world leaders descend on Manhattan.

James Lewis, cybersecurity researcher at Washington’s Center for European Policy Analysis, told the outlet the list of countries capable of such an operation was short, including Russia, China and Israel.

The hidden network was found as part of a sweeping Secret Service probe that kicked off in the spring following telecommunications-related threats targeting senior US government officials, according to investigators.

When agents ultimately raided the locations, they uncovered rows of servers and shelves stacked with SIM cards – including more than 100,000 that had already been activated, as well as a large number still waiting to be deployed, McCool said.

McCool warned of the havoc the network could have caused if it had been left intact — comparing the potential impact to cellular blackouts that followed the 9/11 terror attacks when networks crippled under the strain.

Officials said they haven’t uncovered a direct plot to disrupt the UN General Assembly but noted there was no ongoing threat to the Big Apple.

Investigators are still probing who is responsible but believe perps from certain countries used the system to send encrypted messages to organized crime groups, cartels and terrorist organizations.

Forensic analysis is still in its early stages, McCool said.

“We need to do forensics on 100,000 cell phones, essentially all the phone calls, all the text messages, anything to do with communications, see where those numbers end up,” he said.