Investigators on Thursday were studying surveillance video as they searched for two men who robbed an armored truck of $1.8 million in Southern Florida .

The armed robbers stole the cash from an AT Systems truck as it delivered money to E-Z Checks Cash at a strip mall in Hialeah Gardens on Wednesday, police said. Shots were fired, but no injuries or arrests were reported.

Police and the FBI were not ruling out that the heist was an inside job and were eyeing former and current employees of the delivery business, as well as of the check-cashing business.

The men approached the two guards who were with the vehicle, police Lt. Carlos Fojo said. Local news station WPLG-TV reported that while one guard remained in the truck, the other left the car to bring the money bag to the check-cashing store.

A man then approached the guard and pointed what the guard said felt like a handgun to his back. The man told the guard in Spanish to walk over to a car that was parked and throw the money in the back seat.

WPLG reported that a slight struggle ensued, according to police, when the robber tried to take the gun away from the guard. When the robber failed, he got into the car.

Fojo said Wednesday at least two shots were fired during the 8:30 a.m. robbery but it wasn't immediately clear who fired them.

But footage from a surveillance camera shows one thief pushing the money delivery man away from the armored truck and toward the getaway car. After the delivery man is let go, he fires three rounds at the fleeing getaway vehicle, which all hit the asphalt.

Video also caught a picture of a man wearing dark black sunglasses underneath a hat entering a nearby store just before the heist.

Florida police are looking for a dark blue Mitsubishi. Suspects are considered armed and dangerous. Fojo said more than $1 million in cash was stolen but he wouldn't give an exact figure.

The FBI questioned and released the two guards and were analyzing surveillance video, Fojo said. Witnesses said they saw an altercation between the guards and the robbers.

The FBI and AT Systems Inc., which describes itself as a cash logistics company, did not immediately return calls seeking further detail.

Hialeah Gardens is just northwest of Miami.

Anyone with any information is asked to call the FBI at (305) 944-9101.

The Associated Press contributed to this report.