Hong Kong International Airport cancelled all flights on Monday as thousands of protesters descend on the location to campaign against a proposed extradition bill and police treatment of protesters.
Crowds claim the police have been using excess force to control protesters during previous rallies.
Passengers have been told not to travel to the airport, which is one of the busiest transport hubs in the world.
More than 160 flights scheduled to leave after 18:00 local time will now not depart.
Officials are working to reopen the airport early on Tuesday morning, a statement said.
As rumours spread that police plan to move in on protesters on Monday evening, thousands opted to leave on foot.
There are large backlogs for transport back into the centre, local reports say.
While protests in the city have turned increasingly violent, there were no reports of arrests during the three previous days of the airport sit-in.
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