What we know so far about deadly fire at Canadian military baseImage source, ReutersImage caption, The busy training base is located behind fences on remote land in AlbertaByJack BurgessUpdated 1 hour agoA huge fire swept through a Canadian military base on Saturday, killing at least four people and leaving 19 people in critical condition. Prime Minister Mark Carney described it as one of the worst peace time tragedies on Canadian soil in the history of the military.

Here is what we know about the deadly incident so far. How did the fire start?

The fire at Canadian Forces Base Wainwright broke out at around 16:00 local time (22:00 GMT). Major-General Wade Rutl and, Commander of 1st Canadian Division, said a grass fire ignited on a training range and "uncommonly strong winds caused it to spread rapidly and shift direction" towards soldiers taking part in exercises.

He said the cause of the initial fire remains under investigation. Earlier, local media reported it may have been started when a gas main was struck during a live firing exercise, but the military later said that investigators do not believe any explosions were caused by oil or gas infrastructure.

Figure caption, Carney: ' Canada must now serve' service members killed in fireHow many people have been killed? Four service members are confirmed to have died, while a further 39 people are in hospital - 19 of whom are in critical condition.

Officials have not indicated whether or not the government expects the death toll to rise but said many people had suffered severe burns. On Saturday evening, Royal Alexandra Hospital in Edmonton declared a code orange - a disaster response protocol for a high-casualty incident.

It was stood down on Sunday afternoon. Alberta's health service said the emergency response lasted for 10 hours, and involved 22 ambulances and eight aircraft.

Ongoing care for the injured is expected to be "intensive", a statement continued. A stream of ambulances were seen arriving at the hospital and one doctor told Canadian public broadcaster CBC that the facility had been "completely overwhelmed" by the number of patients.

Where is the base? Canadian Forces Base Wainwright is located in a rural area of the western province of Alberta - around 120 miles (193km) from Edmonton and 180 miles (290km) from Calgary, the province's two largest cities.