Authorities were searching for two black-clad men wearing masks who robbed an armored truck and got away with $1 million in an apparently well-designed holdup.

FBI Special Agent Mark White said investigators are "vigorously pursuing" the robbers, who officials believe also included a third person.

A Loomis armored truck with two guards, one of whom was armed, arrived Wednesday morning at a Compass Bank in East Dallas, authorities said.

One of the guards told investigators that he was unloading the contents of the truck onto a cart when a blue van stopped nearby. The side door of the van opened, and two men in black wearing masks approached him and demanded money. They were carrying what appeared to be semiautomatic rifles.

A second guard, who was driving the armored car, told police that he saw the other guard run down the sidewalk and followed in the truck.

When the guards returned, the suspects and the money that was being loaded on the cart were gone, the report said.

Later, police found the van in a nearby library parking lot, where a witness told police he saw the suspects unload something from the van into another vehicle. A police report showed the van was stolen in June.