Sarnia-Lambton's total number of confirmed COVID-19 cases hit the 400 mark Saturday.
In its daily update, Lambton Public Health reported three new cases, 358 recoveries, up one, and 25 deaths, bringing the number of active cases to 17.
It was reported Friday that there are now three students at St. Patrick's High School who have tested positive. Three classes are closed but the school remains open.
There is still one patient with the virus at Bluewater Health with 16 patients in hospital with tests pending which includes pre-surgical screening.
Sarnia-Lambton is the only region in southwestern Ontario that remains at the lowest "green" standard measures level in Ontario's colour-coded COVID-19 response framework.
Ontario reported 1,588 new cases of the virus Saturday and 21 more deaths.
There are 522 new cases in Peel Region, 450 in Toronto and 153 in York Region.
Peel and Toronto will be in lockdown mode beginning Monday for at least 28 days.