VALLEJO, Calif. (AP) _ Gunmen robbing an armored car company warehouse killed three workers execution-style before dropping bags of loot and fleeing when other employees stumbled onto the holdup, an official said Thursday.

A special state Justice Department team helped police comb the warehouse and surrounding area, and the FBI also was called in to assist in the investigation of Wednesday night's killings, Police Chief Jerry Galvin said.

Investigators have determined that two or more gunmen were involved in the at the Loomis Armored Inc. warehouse, where drivers drop off money collected on their runs for deposit in banks, Galvin said.

A preliminary audit showed that no money was missing from the warehouse, police Chief Jerry Galvin said at a news conference. He said the assailants apparently dropped several bags of cash in a hasty escape.

Loomis officials announced a $150,000 reward for information leading to the arrest and conviction of the killers.

The cold-blooded nature of the killings puzzled police, Galvin said.

''I can say they were executed. They were defenseless at the time they were shot. You can conclude from that that they were bound,'' Galvin said. ''As to why they were executed, I can't even speculate on that sort of an atrocity.''

The robbery was interrupted when another truck pulled up, Galvin said.

Through an open warehouse door, two drivers returning from a delivery saw an employee lying on the floor and money bags in the doorway. They left the scene and called police, Galvin said.

Galvin declined to release any other information provided by the witnesses, saying it could jeopardize the investigation.

Loomis officials declined to discuss the details of the company's day-to- day operation.

The dead were identified as Dennis Jacobson, 29, of Vallejo; Alphonso Lontayo, 25, of Vallejo; and Martin McCumber, 49, of Fairfield, who died at the hospital.

A Loomis truck was the target of robbers in Fresno in September, when two men fatally shot a Loomis guard as he delivered money to a check-cashing outlet. Two men were arrested.