TORONTO (Reuters) - Deaths linked to a heat wave in Canada’s Quebec province has nearly doubled to 33 from the last count, health officials said on Thursday, as extreme weather conditions that have gripped central and eastern Canada reached their peak.

Canada’s weather department added smog warnings for certain areas of the province on Thursday, when the heat wave is forecast to end.

Eighteen of the victims were in Montreal, while the rest died in areas across southern Quebec, the officials said. The people who died were living out of bounds and often vulnerable due to conditions such as substance abuse, chronic ailments and mental illnesses, they added.

Montreal previously raised the city’s response level to “intervention” from “alert” after a spike in heat-related calls to the government’s health information line and for ambulances.

Heat warnings were also issued for much of Ontario, Nova Scotia and New Brunswick.