Ships are skipping Hong Kong for re-fueling after the city implemented strict quarantine regulations at its port to curb the spread of the coronavirus, leaving bunker fuel traders reeling from slumping sales.

For some suppliers, sales have halved this month compared with July, according to people familiar who asked not to be identified because they’re not authorized to speak to the media. Vessels are calling at other ports to refuel, including nearby Shenzhen and in South Korea, said Simon Neo, executive director at marine fuels consultant SDE International Pte.

Hong Kong implemented the rules that took effect at the start of this month after a fresh outbreak flared in the city. It’s requiring crews on vessels that are only calling to refuel and not loading or offloading cargo at the port to undergo a 14-day quarantine in a bid to curb the transmission of the virus.

The number of vessels entering Hong Kong waters each day in the first two weeks of August was around 12, compared with an average of 27 a day in July, according to vessel-tracking data compiled by Bloomberg. Ship fuel sales in August may drop 30% from a month earlier, according to SDE’s Neo. Hong Kong is one of the top five Asian ports in terms of annual marine fuel sales volume