An investigation by the U.S. Secret Service dismantled a massive network of electronic devices in and around New York City, which posed “an imminent threat to the agency’s protective operations,” the agency said in a Tuesday press release. “The potential for disruption to our country’s telecommunications posed by this network of devices cannot be overstated,” said U.S. Secret Service Director Sean Curran.

The network included more than 300 SIM servers and 100,000 SIM cards organized in large banks and distributed across multiple sites. Investigators also found many SIM cards still waiting to be deployed, enough to double or triple the network’s capacity, according to Matt McCool, the special agent in charge of the Secret Service’s New York field office.

These SIM cards could act as banks of mock cellphones, able to generate a massive number of calls and texts, which could overwhelm local cellular networks, McCool said. The operation had the capacity to generate 30 million text messages per minute.

The SIM card banks also allowed operators to mask encrypted communications, potentially allowing conversations related to criminal activity or national security risks to go undetected.

McCool described the operation as “absolutely well-funded and well-organized,” saying that the hardware alone cost millions of dollars. For this reason, as well as preliminary forensic analysis, investigators believe the network hosted “cellular communications between nation-state threat actors” and known criminals.

The Secret Service discovered the sites as part of a protective investigation into “multiple telecommunications-related imminent threats related to senior U.S. government officials this spring,” said McCool.

Through cooperation with other law enforcement agencies, the investigation led the Secret Service to the New York City area, where the Secret Service discovered the sites around the same time that the U.N. General Assembly opened its annual meeting in Manhattan. According to the Service, the devices were concentrated within 35 miles of the U.N. headquarters.

“Given the timing, location, and potential for significant disruption to New York telecommunications,” explained the Secret Service, the service’s Advanced Threat Interdiction Unit moved swiftly to dismantle the threat, instead of waiting to capture those who assembled it. “This investigation is currently ongoing.”

“The U.S. Secret Service’s protective mission is all about prevention,” said Curran, “and this investigation makes it clear to potential bad actors that imminent threats to our protectees will be immediately investigated, tracked down and dismantled.”

Yet the ongoing investigation suggests that the potential for other threats remains ongoing as well. “Could there be others?” asked McCool. “It’d be unwise to think that there’s not other networks out there being made in other cities in the United States.”