York Regional Police are investigating four separate fires Monday morning in the Yonge and Langstaff area.
They are believed to be suspicious.
Police say the fires started at businesses in the area including a roofing company, a paving company, a car carrier company and a junk yard.
They say a resident nearby called 911 around 4:10 a.m. after hearing explosions.
Three homes in the area were evacuated.
Anyone with information is asked to call York Regional Police.