The union representing Waterloo Region paramedics issued its fourth code red of the week on Friday evening.
It was called just before 8 p.m.
CUPE 5191 announced the code red on twitter, and said that there were zero ambulances available for over 600 thousand people.
There had previously been a code red on Tuesday, and two more on Thursday in the region.
It follows several other code reds in the month of September.
CUPE 5191 has continuously called on the provincial, and municipal governments for more resources, and support.