Hong Kong police launched a fresh crackdown Tuesday on Uber, arresting 21 drivers suspected of working for the ride-hailing giant in the Asian financial center.

It's the latest regulatory headache for Uber, which already is fighting a similar case in Hong Kong.

The drivers were arrested in an undercover operation on suspicion of carrying passengers for hire and not having third-party insurance for their cars, said Chief Inspector Lau Tat-fai.

Lau said the 20 men and one woman aged 21 to 59 were taken into custody and their vehicles impounded.

"I would like to emphasize that police are still continuing their enforcement action and I can't rule out the possibility of more drivers being arrested," he told reporters.

Lau, who did not specifically mention Uber, said anybody who "assisted or instigated" drivers might also be legally responsible. He called on people using smartphones to arrange rides to make sure that drivers have the proper vehicle hire permits.

"We are extremely disappointed by the police enforcement today. We stand together with the 21 driver partners," Uber said in a statement, adding that it would help them and provide legal support.

The San Francisco-based tech company said it has a ridesharing insurance policy that complies with Hong Kong legal requirements and covers up to 100 million Hong Kong dollars ($12.8 million) in liability.

"Ridesharing should not be a crime. Hong Kong is an international city known for its embrace of global economic trends and new technologies but current transportation regulations have failed to keep up with innovation," it said.

In March, a Hong Kong court convicted five Uber drivers on the same charges and fined them HK$10,000 ($1,284) after they were arrested by undercover police. The company said it would stand by the five drivers, whose sentences were suspended after they launched an appeal.

In 2015, police searched Uber's Hong Kong offices and confiscated computers and documents.