Police said that the drivers were arrested Tuesday in an undercover operation on suspicion of carrying passengers for hire and not having third-party insurance for their cars. The police said the 20 men and one woman were taken into custody and their vehicles impounded.
They said they were continuing their enforcement action and couldn't rule out further arrests.
Police did not specifically mention Uber, but company representatives said they planned to issue a statement.
In March, five Uber drivers were convicted on similar charges in a Hong Kong court.