The leading edge remained in a large agricultural parcel that included another house, which was about 100 yards (91 meters) from the lava, Oliveira said.
Dozens of homes, business and other structures are in the area of the lava flow. That amount could increase as the flow front widens.
So far lava has burned a garden shed, tires and some metal materials.
On Wednesday, it burned mostly vegetation, while the rain helped tamp down smoke from the crackling stream. Officials are monitoring hazards from the smoke. Chemists from the observatory detected only low levels of sulfur dioxide, Oliveira said.