Federal authorities have arrested two additional men, bringing the total to seven, in a foiled plot to attack the UFC Freedom 250 event at the White House on June 14.The conspirators allegedly planned to use explosive-laden drones and snipers to target guests, including Donald Trump and Mark Zuckerberg, during the anniversary celebration.The investigation, which also uncovered threats against a FIFA World Cup event, continues under the oversight of the FBI and the Department of Justice.Prosecutors claim the suspects utilized encrypted communications to coordinate the purchase of firearms and 3D-printed equipment before being thwarted by a tip from a suspect's mother.