Armed robbers stole $4m in gold on Sunday from a truck traveling from Florida to Massachusetts, authorities said on Monday.

The two security guards working for Transvalue Inc of Miami reported pulling off to the side of the interstate highway about 6pm on Sunday after their vehicle began having mechanical problems, the sheriff’s office said.

They were then approached by three armed men driving a white van who ordered the guards to lie on the ground, tied their hands behind their backs and then marched them into nearby woods. The robbers then unloaded barrels filled with gold and made their getaway, according to a statement.

The office of Sheriff Calvin Woodard Jr did not respond to messages seeking additional information, such as the type of vehicle the gold was being hauled in or what type of weapons were used. No detailed description of the suspects or their vehicle was released.

Shelley Lynch, spokeswoman for the Federal Bureau of Investigation’s Charlotte field office, said agents are assisting the local sheriff and are working to determine whether a federal crime has been committed.

Messages seeking comment from Transvalue were not immediately returned. According to its website, the company specializes in transporting cash, precious metals, gems and jewelry in armored trucks.