A quick-thinking resident raised the alarm when he spotted a blaze this morning (Thursday).
The fire broke out just before 8am at the rear of a property in West View, Clitheroe.
Clitheroe Fire Station Watch Manager Dave McGrath said the blaze started at the rear of a mid terraced house and quickly spread to a nearby oil storage tank.
He said: "Everyone was in bed but one of the residents heard a noise outside and spotted the fire.
"He managed to alert other neighbours so they could leave their properties. The fire developed very quickly and caused severe damage to two of the houses and heat damage to the windows of two other houses. A conservatory at one of the properties was destroyed by the blaze."
Two fire engines and crews from Clitheroe and one engine and crew from Hyndburn wearing four sets of breathing apparatus tackled the flames using two hosereel jets.
Watch manager McGrath added: "There were a number of pets in the properties but none of them came to any harm.
"Due to the nature of the fire there was a great deal of thick, black smoke that could be seen for miles around."
Firefighters spent three hours at the scene. It is believed the fire started accidentally.