Singapore and Hong Kong called off an announcement planned for Thursday on an air travel bubble between Asia’s two major financial hubs, according to people familiar with the matter, the second time in five months the highly anticipated arrangement appears to have run into obstacles.

No reason was immediately provided on why the announcement -- which Bloomberg reported Wednesday was expected as soon as Thursday -- was postponed and a new date has not been set, said the people, who asked not to be identified as they’re not authorized to speak publicly. The cancellation was initiated by the Singapore side, one of the people said.

Singapore’s Ministry of Transport and Hong Kong’s Commerce and Economic Development Bureau didn’t immediately respond to requests for comment.

Singapore and Hong Kong have been working on trying to revive their bubble plans after a previously scheduled November start was shelved due to a virus flareup in Hong Kong. The new start date for the bubble was planned for May, people familiar have said, though that’s now uncertain. While it’s unclear what triggered the postponement of the announcement, it comes as Singapore faces new virus cases among its migrant worker community, which underpinned the city’s major outbreak last year.

Reopening to international travel is key for Singapore and Hong Kong, which don’t have domestic travel markets.

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Singapore Transport Minister Ong Ye Kung said earlier this month that he hopes an agreement on the air travel bubble would be announced “soon,” echoing Hong Kong’s Chief Executive Carrie Lam’s earlier comments.

In an announcement Wednesday, Singapore eased quarantine rules for those travelling to Hong Kong. Travellers from Hong Kong will have to stay in home isolation for seven days upon arriving in Singapore, down from a previous rule of 14 days in a government-chosen hotel.

There are now concerns that a resurgence of the virus in Singapore could upend the easing plans. The city, which saw a massive outbreak among its army of low-wage migrant workers last year, said Thursday that 11 workers at Westlite Woodlands dormitory had tested positive for Covid-19.

Among them, 10 had previously been infected and recovered, said a government statement. The flareup raises fears that virus is again circulating among the workers, who live in close conditions in accommodation segregated from the wider community. Their movements are highly restricted by the government, though the rest of the population has seen social and economic activity normalize after Singapore contained its outbreak last year.