Health authorities have reported at least nine more confirmed Covid-19 cases linked to an area in the Yau Tsim Mong district, raising the number of cases detected there to 99.

The nine were among 55 new infections reported on Sunday – all but four were locally-acquired cases.

16 of the local cases were untraceable.

Many people from the area are also among more than 80 preliminary positive cases, meaning Hong Kong could on Monday see the highest daily caseload this year.

Three of the nine patients from the Yau Tsim Mong cluster are cleaners hired by the Food and Environmental Hygiene Department to maintain public toilets in the area.

Chuang Shuk-kwan from the Centre for Health Protection said while it’s possible that the cleaners had cross-infected one another, the toilets could also be a source of transmission.

Since last week, officials have issued mandatory testing orders to residents of 20 blocks in the Yau Tsim Mong area, including those living in an old tenement building on Reclamation Street where more than 20 cases had been detected.

Many residents have rushed to take tests over the weekend ahead of a Monday deadline.

Chuang said residents of eight more buildings in the vicinity will now be required to undergo testing.

She also expressed concern that more people from the area are among the dozens of preliminary positive cases that have been reported.

“It is possible that due to compulsory testing, more local residents know about this test and came forward for testing; hopefully we can investigate them and break the spread. But of course the sheer number of cases, so many cases, is a concern, because any one of them may cause a major outbreak in the community.” Chuang said.

The CHP said mandatory testing orders would also be issued to residents of a block in Lido Garden in Sham Tseng and On Tai Mansion in Hung Hom, after four cases were found in each of the blocks.

Meanwhile, officials said around 80 staff and residents of a care home for the elderly in Sham Shui Po have been sent to quarantine, after an 87-year-old female resident was confirmed with the coronavirus.