That came after the Food and Health Bureau issued a set of guidelines to bar operators on Wednesday, specifying that patrons must jot down their names and the dates and times of their swabs on their test kit before taking pictures of them to show to bar operators.

The bureau also urged people to avoid bringing the tests along or administering the test on-site. The Centre for Health Protection's principal medical and health officer, Albert Au Ka-wing, echoed these sentiments, saying people should get tested at home to ward off transmission risks.

Many heeded Au's warning in Lan Kwai Fong yesterday evening, with people preparing photos of their negative test results in advance. One bar manager said he would also check the metadata for the date of creation to ensure people aren't using old photos.

Although the manager acknowledged patrons aren't encouraged to get tested on site, he admitted they would offer test kits to those who forgot to do them at home.

The manager of another bar in the area expects to lose half his business due to the new requirement, adding bar visits are often spontaneous in nature and most would not prepare test results in advance. As such, he said, his bar had got 200 test kits ready for customers.

A restaurant manager nearby also said she would provide test kits to customers, citing worries that business would be affected if people aren't allowed to test on site. The worries aren't only limited to customers as some restaurant owners said authorities failed to explain whether they are subject to the mandate as well.

Some establishments in Causeway Bay were found to have ignored the requirement altogether. It is understood at least five bars and restaurants allowed people to enter without checking for test results first.

Among bar-goers, the new requirement gave rise to some confusion.

"We didn't know we had to take a rapid test beforehand," one man said, adding he had no choice but to test on site with the kits offered by the bars.

"People aren't going to do the test every day just because they might have a glass of beer later," he said.

Another man criticized the new requirement as troublesome, saying he won't visit bars as often now. The virus can be transmitted anywhere, he added, noting bars should just be shut down if authorities wish to curb transmission instead of the current half measure.

However, one bar-goer said the requirement doesn't impact him since he's required to get tested every day for work anyway.

Ricky Chiu Yin-to, founder of biochemical company and test-kit manufacturer Phase Scientific International, suggested mobile rapid test stations be set up near bars. It is imperative people don't administer the tests outside bars since they have to remove their masks, Chiu said, adding the sneezing that often accompanies a nasal swab poses a severe transmission risk.