Details emerging from the theft of nearly $5 million in gold bars on an interstate highway indicate the heist was carefully planned and raise questions about who was involved other than the three armed robbers.

The robbers pulled up almost immediately after the drivers made an unscheduled stop on a dark stretch of highway in North Carolina, according to a warrant. When the crew got out of the truck, they left their firearms behind in violation of their employer's security rules, the sheriff said. And while the workers told authorities they had to pull over because strong gasoline fumes were making at least one of them sick, a mechanic found no problems with the truck.

The circumstances led one detective to write that the heist on Sunday "could be an inside job," though the sheriff declined to commit to that theory during a news conference Wednesday. One thing was clear, though: The heist was targeted and planned, down to the orange traffic cones the robbers put out while they unloaded 275 pounds of gold worth $4.8 million.

Asked to put the case into context, Wilson County Sheriff Calvin Woodard, who's a native of the area, remarked: "It's different."

"We want to make sure that all the citizens, as well as those who live outside the county, feel safe when they travel that stretch of highway."

On Wednesday, authorities released search warrants for the truck and the drivers' cellphones filed the day after the heist in which detectives wrote of their suspicions.

"The fact that the truck was robbed immediately upon pulling over at an unannounced stop is suspicious in and of itself," the warrants state, adding that the truck had no external markings betraying the cargo. The warrant said the suspects tried to steal the truck but could not get it started, indicating they did not know how to operate a commercial truck.

Woodard said the guards were still considered victims, not suspects, but that all possibilities were being investigated.

Asked to elaborate on the suspicions mentioned in the warrants, the sheriff said they were written in a hurry before the victims, who spoke little English, could be thoroughly interviewed in Spanish.

The strange scene unfolded around dusk Sunday in a rural area about 50 miles east of Raleigh.

Earlier in the day, the guards had stopped for gas in Dillon, South Carolina, near the North Carolina line. As they kept driving, one of them started to feel sick and said he smelled gas, Woodard said. A warrant says they pulled over so the man could vomit.

As soon as the guards stopped on the shoulder, three robbers drove up in a cargo van and confronted them at gunpoint, yelling "Policia!" and ordering the crew to lie on the ground.

The guards got out of the tractor-trailer without their guns, according to the sheriff, who said it was a company security violation to leave the truck without their weapons.

The robbers tied their hands behind their backs and marched them into nearby woods, authorities said. Woodard said the robbers cut a padlock, but there were no other security measures to stop them.

He said that after deputies arrived, a mechanic found no problems with the truck.

The heist happened hours after the truck left Miami for a town south of Boston.

Neither guard was injured, according to their employer, Miami-based Transvalue Inc., which specializes in transporting cash, precious metals, gems and jewelry. A Transvalue spokeswoman said she would seek comment from company's executives about the details in the warrants.

The company has offered a $50,000 reward for information leading to an arrest. The company says its shipments are insured for up to $100 million.

One warrant says the owner of the cargo was Republic Metals Corp. of Opa-locka, Florida. An attorney for the company did not return a telephone call seeking comment late Wednesday.

After the thieves escaped with the gold, the guards were left stranded along Interstate 95 until they drew the attention of startled motorists. Several called 911 to report seeing uniformed men running into the highway with their hands bound, motioning for help.

"They've got their hands zip-tied behind their backs, and they're out in the road to try to flag people down to call the police," one caller said.