The fire broke out at the back of the homes in the hamlet of Weston on the edge of the town.
Neighbours who saw smoke coming from the back of the houses next to Weston Mill, alerted those living inside and they were able to get out safely.
Fire crews from across Shropshire dealt with the blaze and stopped it from spreading even further. It took two-and-a-half hours to bring the fire under control.
Today experts were looking at possible structural damage to the properties.
The blaze broke out just before 2.30am and involved a semi-detached property and a neighbouring house.
Two fire crews from Oswestry were first on the scene and were joined by one from Ellesmere and the aerial ladder crew from Shrewsbury.
Fire service watch manager, Andy Armstrong, said six firefighters put on breathing apparatus to go into the properties to fight the blaze while others trained jets from the aerial platform overhead onto the fire.
"It was an oil tank fire which spread to property, in the roof space," he said.
"The occupants were alerted by neighbours who saw the smoke coming from the back of the homes."
Water was ferried from a nearby water hydrant and the lanes in the Weston area were closed to traffic to allow the firefighting and clean up operation to go ahead.
The semi-detached property had recently been renovated.
Mr Armstrong said: "It was renovated to an unusual design, with bedrooms on the ground floor and the living accommodation above. It also has a modern cavity wall which we had to take into account. The fire service has to adapt all the time to building design."
Firefighters were still on scene at 11am, carrying out salvage work inside the houses, including removing damaged tiles and charred door frames. Relief crews arrived from Shrewsbury and Wem.
"We have a structural specialist arriving to look at whether there has been any structural damage," Mr Armstrong said.