(CNN)The FBI arrested three alleged members of a white supremacist group early Thursday, including two men accused of possessing a machine gun, over 1,000 rounds of ammunition and body armor parts, according to the Justice Department.
FBI arrests 3 alleged white supremacists. They planned to attend Virginia pro-gun rally, official says
The three were arrested at residences in Delaware and Maryland and taken into custody without incident, FBI spokesman Dave Fitz said.
The men, who the Justice Department says are members of the international white supremacist group known as The Base, were believed to be planning to attend a pro-gun rally in Virginia's capital of Richmond on Monday that is expected to draw a significant crowd of extremists, according to a law enforcement official.
They're charged with multiple firearms and immigration-related offenses and at court appearances Thursday afternoon, a federal judge ordered that the men remain in custody ahead of a detention hearing next week.
Brian Mark Lemley Jr., 33, is accused of transporting a machine gun, as well as transporting a firearm and ammunition with intent to commit a felony.
Lemley and William Garfield Bilbrough IV, 19, are also accused of transporting and harboring an alien -- 27-year-old Patrik Jordan Mathews, a Canadian citizen and former combat engineer in the Canadian Army Reserve.
Like Lemley, Mathews is charged with transporting a firearm and ammunition with intent to commit a felony. Mathews is also charged with being an alien in possession of a firearm and ammunition.
The Washington Post first reported the arrests.
Mathews is accused of illegally crossing into the US -- specifically, Minnesota -- from Canada on August 19.
Federal authorities in Canada had reported Mathews as a missing person as of late August. Royal Canadian Mounted Police said in September that they had found a car belonging to Mathews abandoned at a rural property in the border town of Piney, Manitoba.
A Winnipeg newspaper ran a story over the summer alleging Mathews was recruiting for The Base. A spokesman for Canada's Department of National Defence told CNN Mathews was relieved of his military duties in early August as a result of the "seriousness" of allegations against him "and the risk to unit morale and cohesion."
On August 30, Lemley and Bilbrough allegedly drove some 600 miles to pick up Mathews in Michigan, according to the complaint filed in the Maryland federal court.
Lemley and Mathews, who were arrested together in Delaware, smashed their cell phones and dropped them in the toilet before they were taken into custody, a prosecutor alleged in a hearing Thursday.
At brief appearances in Maryland federal court, the men were ordered to remain in custody ahead of a detention hearing set for Wednesday.
The third man arrested Thursday, Bilbrough, will also remain in custody ahead of a Wednesday detention hearing after his attorney lost a challenge to the prosecutor's claims that Bilbrough posed a "serious risk of flight" who could attempt to obstruct justice if he were to be set free.