South African police say they seized a rocket head and arrested two men in a raid in downtown Johannesburg.

Police said in a statement Thursday that agents, acting on a tip about a sale of explosives, found a South African and a Mozambican sitting in a Mercedes Benz on Wednesday night. They say they searched the vehicle and found the rocket head, valued at about $730,000. There were no immediate details on the type of rocket.

Police also questioned three men in a nearby vehicle after they searched it and found diamonds believed to be of foreign origin. It was unclear whether the men with diamonds were linked to the men with the rocket head.

Authorities say they expect to make more arrests.