Dunedin Hospital's Covid-19 ward is on the same floor but separate from 7C .
No staff have since tested positive, but surveillance testing would continue both for them and for patients.
For now, no further patients are being admitted to 7C.
"Affected patients and their whanau are being kept informed of the situation," the spokeswoman said.
This is the third Covid scare in SDHB facilities since the Omicron outbreak began.
Earlier, cases were detected in a mental health ward at Wakari Hospital and a gynaecology ward at Dunedin Hospital.
The four cases in Dunedin Hospital were among 1212 new community cases reported in the South yesterday.
Of those, 343 were in Dunedin, 295 in Invercargill, and 185 in Queenstown-Lakes.
Covid-19 hospitalisation rates continued to creep up in the region.
Dunedin Hospital had 16 patients, two of whom were in intensive care, while Dunstan Hospital had one patient and Southland Hospital had eight.
SDHB medical officer of health Susan Jack urged people who had not yet got a booster dose of the Covid-19 vaccine to do so.
Nationally, 15,235 cases of Covid-19 were reported by the Ministry of Health yesterday.
A further 22 Covid deaths were reported - all but four from Canterbury were in the North Island.