The blaze started in a two-storey house on Lees St before spreading to a neighbouring single-storey home and what looked like a fence to an adjoining property.
Firefighters were working to prevent the fire spreading to adjacent properties.
In an update, Underdown said that heavy machinery was now on site and fire crews were preparing for a final extinguishment.
“One truck and two investigators are on site and crews are still waiting for a council staff member,” he said.
Firefighters battle a fire that has spread to two homes in Lees St, Milldale.
Residents on social media posted about the “huge fire” and sympathised with the “poor families” involved.