() Investigators are still piecing together who was involved in a massive threat to New York City’s telecommunications network.

The U.S. Secret Service announced it thwarted a plot that, if successfully carried out, would have jammed cell towers and blocked phone service for millions of Americans. It happened just as dozens of world leaders arrived in Manhattan for the 80th U.N. General Assembly.

More than 300 servers and 100,000 SIM cards were seized from five different sites, all within 35 miles of the United Nations.

“This was a case that began as a protective intelligence investigation threat case, and what they uncovered was a major network of telecommunications devices that can be used anonymously and encrypted that can be used to shut down cell towers, not allow access to EMS and 911,” Matt McCool, special agent in charge of the Secret Service’s New York field office, said. “We do know that nation-state threat actors or foreign governments are communicating with criminals in the United States.”

Authorities said the issue is no longer a threat; however, they said there may be other cells just like this in other parts of the U.S.

The threats are called SIM farms, systems capable of sending out 30 million text messages in a matter of 12 minutes, according to Wired.

“It can’t be understated what this system is capable of doing,” McCool said. “You can’t use Waze, text messages, and if you coupled that with some other event associated with UNGA, it could be catastrophic to the city.”

SIM farms were originally developed as a way to conduct low-cost, international calls. Now, officials say it’s being used by fraud organizations to try and target mass audiences, like what is seen with phishing calls and texts that many people get each day.