An early morning fire in Saskatoon has caused about $50,000 in damage.

At around 1:40 a.m. CST, the Saskatoon Fire Department responded to a call of smoke coming from an apartment complex on the 1300 block of 20th Street W. 

A mattress had caught fire in the building and its occupants were forced outside.

Ventilation fans were put in place to clear the smoke after firefighters were able to put out the fire with the help of an existing water sprinkler head.

The cause of the fire is undetermined at this point.