Hong Kong said it would ban flights from India, Pakistan and the Philippines for two weeks starting on Tuesday after detecting its first local case involving a variant of the coronavirus.

A man who tested positive on Friday, after returning from Dubai and then completing his mandatory 21 days of quarantine, is the Asian financial hub’s first case outside quarantine found to carry the N501Y spike mutation. This change appears to help the virus bind to cells and occurs in several variants that have spread rapidly around the world, including B.1.1.7, first detected in Britain.

On Sunday, a friend the man had stayed with after quarantine also tested positive for the virus, with a preliminary positive for the N501Y mutation. Though other residents of the building tested negative, the authorities ordered about 80 of them to quarantine at a government facility.

The N501Y mutation has been a focus of the Chinese territory’s efforts to keep out coronavirus variants: The India, Pakistan and Philippines travel bans came under a policy announced last Wednesday blocking flights from any country whose Hong Kong arrivals yielded more than five positive tests for the mutation within seven days. In the neighboring Chinese territory of Macau, the quarantine requirement for arrivals from India, Pakistan and the Philippines was extended on Monday to 28 days from 21.

Hong Kong already requires negative test results before boarding and upon arrival before travelers are allowed to settle into their quarantine hotels. Out of the 175 new coronavirus cases reported in Hong Kong over the past two weeks, 132 of them were classified as imported.