North Carolina investigators are trying to determine how $4.8 million worth of gold bars were stolen from a secured truck on a highway on Sunday, CNN reported.

Even more of a mystery is how the security guards in the truck, both of whom were armed, ended up being ambushed, tied up and led off into the woods while the thieves made off with the gold.

"There's suspicion about everything going on in this case," Wilson County Sheriff Calvin Woodard Jr. said Wednesday.

Both security guards, employed by Florida-based TransValue Inc., said the incident occurred after they left Miami with 275 pounds of gold in the padlocked truck. They were headed for Bridgewater, Massachusetts, "to a place...where they handled such things," Woodard said, according to CNN.

The guards were in Wilson County, N.C., when they said they smelled gas inside the truck and pulled over on Interstate 95 after one guard complained of feeling sick, authorities told CNN.

As soon as the sick guard exited the truck, he was ambushed by two suspects who yelled "Policia," forced to the ground and bound with three zip ties. They bounded the second guard with duct tape after he got out of the truck, Woodard said.

TransValue, which specializes in transporting valuable cargo, requires workers to keep their firearms on them when exiting the vehicle. Neither guard was armed during the ambush.

After they were bound, the suspects, three in total, abandoned their captives in the nearby woods, stole the gold and fled the scene in a white van, authorities told CNN.

No witnesses called police to report seeing the guards being led by men into the woods. But at around 7 a.m., police received reports of bound men coming out of the woods.

According to the guards, who spoke to police through a Spanish-English translator, there were three suspects involved. Two of them were described as Hispanic males, one of them with a Cuban accent and the other with a mustache and goatee.

Except for a few scratches on their legs, both security guards escaped the heist unscathed, CNN reported.

"Right now, (the guards) are still considered victims," Woodard said. "...But we're investigating every avenue."

He added that TransValue is cooperating with authorities.