A man accused of stealing an assault rifle, shotgun and medical supplies from the trunk of a North Dakota Highway Patrol cruiser is facing federal weapons charges.

Alman Andrew Wong, 32, of Mandan, was arrested Sunday night, in Montana's Mineral County, said Trooper Glenn Quinnell of the Montana Highway Patrol.

"At first, he was cited for driving while revoked. But during the course of the investigation, two weapons were recovered," said Quinnell, who made the traffic stop near Superior, Mont. He said Wong was speeding.

The weapons, a shotgun and an M-14 rifle, were traced to the North Dakota Highway Patrol, which had reported them stolen last week to Bismarck police.

North Dakota Highway Patrol Lt. Mike Gerhart said troopers do not know exactly how long the weapons were missing from the patrol car, which was in Bismarck. They also do not known how someone opened the trunk of the patrol cruiser, Gerhart said.

"It was a matter of an officer who went into the trunk and realized they were no longer there," Gerhart said. "They were discovered missing last week."

Bismarck police, who have been investigating the theft, were told that weapons and medical supplies, including an oxygen tank, were stolen sometime between May 27 and May 30, police Lt. Randy Ziegler said.

The theft may have occurred while the patrol car was parked in front of a Bismarck motel, where a trooper was attending a meeting with other members of the Highway Patrol, he said.

Gerhart said the weapons stolen from the patrol car "more than likely would have been loaded."

Quinnell would not say if the weapons were loaded when they were found in Wong's vehicle. He said Wong was arrested as part of a crime sweep involving several law enforcement agencies, including the U.S. Customs and Border Patrol, and the Immigration and Customs Enforcement.

"We were not targeting anybody in particular," Quinnell said.

ICE agent Steve Stow said Wong is a U.S. citizen with an outstanding warrant in Washington state, but he did not know details. Quinnell said Wong is facing "multiple charges in multiple states."

Wong is being held in Superior, Mont., in the Mineral County jail, is slated to appear in federal court later this week, Stow said Monday.

The U.S. attorney in Montana is prosecuting the case, authorities said.