The FBI thwarted a plot targeting a UFC event that took place on Sunday on the South Lawn of the White House, the agency's head Kash Patel has said.

Multiple suspects were in custody following a "multi-state operation", Patel said in a social media post on Tuesday morning. "Allegedly planned attacks were stopped cold," he added.

Two sources told the BBC's US news partner CBS News that the planned attack would have partly involved using explosive-laden drone aircraft to strike nearby buildings.

A suspect was taken into custody in Cincinnati last week, CBS also reported, and investigators obtained access to Signal chats in which multiple people allegedly discussed the plan.

The BBC has requested further comment from the FBI.

By using the drones, the plotters aimed to spark panic and draw the fleeing crowd toward a sniper team, the sources also told CBS. A "second wave" of attackers would have then allegedly planned to storm the White House gate.

Patel's statement on X did not confirm those details - though he did post a link to a report by Fox News that included them.

"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," Patel added in his post.

The Secret Service worked "closely with the FBI throughout this investigation" and their "formal comments regarding the specifics of this case will be made available in court filings", Secret Service Director Sean Curran said in a statement.

On Sunday, as part of the celebration of the nation's 250th anniversary, the White House hosted a series of Ultimate Fighting Championship (UFC) matches on the South Lawn.

The event coincided with Trump's 80th birthday. Some members of his administration were in attendance, as were some celebrities.