Three armed men are on the run after they allegedly stole $4 million worth of gold from a tractor-trailer rig carrying a shipment along Interstate 95 in eastern North Carolina, police said Monday.

Two armed security guards employed by the transport company, TransValue Inc., reported the robbery around 6:45 p.m. on Sunday to Wilson County sheriff's deputies.

The guards told officers that earlier in the evening, as they were passing through Wilson County about 50 miles east of Raleigh, their truck carrying the shipment of gold and silver had mechanical problems, so they pulled it to the side of the road.

While they were parked, three armed men in a white van approached them, ordered them onto the ground and tied their hands behind their backs, police said.

The men made the guards walk into the woods and then left with several barrels of gold estimated to be worth more than $4 million, police said.

The guards said they were traveling northbound from Miami to Massachusetts.

The case is under investigation by the sheriff's office and the Federal Bureau of Investigation.

Jay Rodriguez, chief executive officer of TransValue, said his company is offering a $50,000 reward for the arrest and conviction of the robbers.

The armored security transport company has 50 employees and a fleet of 20 vehicles, Rodriguez said.