Officers carrying automatic rifles boarded a Cheung Chau-Central ferry when it tied up at Pier 5 of the Central Ferry Piers. Passengers were ordered to remain in their seats and to place their hands on top of seats in front of them.

There had been claims that passengers on the ferry leaving Cheung Chau at 3.45pm for Central had spotted a gun-wielding foreigner on board, and a report went to police.

When the ferry arrived at Central the captain asked all passengers to remain in their seats, then more than 20 armed police searched the ferry as police boats bobbed around and about 10 police vehicles took up positions around the pier area.

"At first we didn't know what was going on, but suddenly we saw about a dozen police officers with guns on board," one passenger recounted. "Then we were told to sit down, keep our hands on the front seat and not to make phone calls. When someone asked what was going on they said they were looking for someone."

But after about 30 minutes' searching there was no suspect identified and no weapon found, and the officers left at around 5 pm.

Then passengers were allowed to disembark.

A Sun Ferry executive said the company had been notified by police about 4pm that officers needed to board and inspect ferries departing from Cheung Chau to Central.

That meant three ferries carrying more than 700 passengers were delayed and had to wait for the police to complete inspections before they could disembark at Central Pier 5.

The incident also led to three ferries departing from Central being delayed.