The wildfires in Fort McMurray, Alta., helped lead to a 25 per cent drop in oilsands production in May, according to the latest data from the Alberta Energy Regulator.

The numbers released Thursday show upgraded and non-upgraded oilsands production for May totalled 48.7 million barrels, down from just under 65 million barrels in April.

The massive wildfires forced producers to shut down crude operations as a precaution, with the full effects on production not yet known since many companies had operations halted well into June and even into July.

Non-oilsands production in Alberta, which escaped the effects of the fire, saw a slight increase in production to 15.2 million barrels of oil.

The impact of the wildfires is showing in quarter results, with Suncor Energy saying late Wednesday it had a net loss of $735 million after failing to produce about 20-million barrels of upgraded and raw bitumen because of the fires.

The Insurance Bureau of Canada estimates the Fort McMurray wildfire to be the costliest natural disaster in Canadian history with about $3.58 billion in damages expected, though oil producers are largely excluded from insurance claims because most facilities weren't damaged.