The FBI and its law enforcement partners have foiled an alleged terror plot targeting last weekend's UFC Freedom 250 event in Washington DC, according to officials.

Five people were in custody as of Monday, and investigators identified 23 people as part of a potential network of plotters. 

Officials said the group planned to use explosive-laden drones to strike buildings near the event, triggering a mass evacuation before funnelling panicked crowds towards a pre-positioned sniper team as they tried to flee.

A 'second wave' was then allegedly planned to storm the White House gate, according to officials.

The FBI first learned of the threat on June 10 and worked with partners to gather enough evidence to make an arrest in Cincinnati, where one suspect was taken into custody.

Investigators later uncovered a series of Signal chats in which members of the alleged network discussed plans to attack the UFC event.

An initial search of one suspect's iPhone revealed at least 23 Signal users allegedly discussing preparations for the operation.

Some of the suspects allegedly planned to travel to Fredericksburg, Virginia, on June 12 and 13 to make final preparations ahead of the attack.

One suspect allegedly told investigators the goal was to target 'capitalist elites,' 'billionaires' or politicians who received donations from the American Israel Public Affairs Committee.

The sprawling investigation involved at least 12 FBI field offices across the US.

FBI Director Kash Patel credited the FBI, the Department of Justice (DOJ) and law enforcement partners with acting quickly across multiple states to prevent the alleged attack.

'Thanks to the rapid action of this FBI, our partners, and the Department of Justice in a multi-state operation, multiple individuals are now in custody and allegedly planned attacks were stopped cold,' Patel said in a statement to Fox News Digital.

Patel said the operation showed the FBI's ability to respond rapidly when threats emerge.

'While the result represented the best of investigative work, it was also nothing out of the ordinary for this law enforcement team,' Patel said. 

'We are built to detect, respond to, and bring to justice those who threaten the lives of American citizens - particularly during large gatherings like the historic UFC 250 fight. That's exactly what we did here.'

'I want to thank our great agents and partners, this work remains ongoing, and we will continue to update the public as permitted,' Patel added. 

The alleged plot targeted UFC Freedom 250, a high-profile White House event held on the South Lawn as part of Donald Trump's 80th birthday weekend.

This is a breaking news story, more to follow.