Officials are investigating, after a massive fire destroyed a number of houses in Fort McMurray early Monday morning.

Officials with Wood Buffalo Emergency Services said firefighters were dispatched to a structure fire on Roy Lane in the Abasand area just before 1 a.m.

When firefighters arrived, they found two homes fully engulfed, and flames were spreading to the roof of a third home.

In the end, the fire destroyed four homes and three detached garages – all of those structures have been classified as total losses. Four other homes have superficial damage, officials said, and a number of others were damaged by radiant heat.

Three vehicles and a fifth wheel were also significantly damaged in the fire.

Officials said 27 firefighters worked through the night to contain the blaze, and crews remained on the scene for several hours.

The cause of the fire is still under investigation.

Officials said RCMP helped to evacuate displaced residents, with help from Victim Services and Emergency Social Services – some of those residents were able to return home.