The force said the three money exchange employees were in a car driving on Hoi Po Road in Yau Ma Tei when they were ambushed by the two suspects, who rear bumped their car.
The duo was said to be armed with hammers and knives when they snatch the two bags carrying cash worth over HK$10 million in total, before jumping back into their car to escape.
The two made their escape in a black BMW SUV, which sped away before officers arrived.
Two of the employees suffered minor injuries, with cuts caused by the shattered car windows.
A police source said the mugging appeared to be well-planned. By 3pm, the manhunt was continuing and no arrests had been made.
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