Austin Fire Chief Dan Wilson said Thursday that the official cause of Wednesday’s house fire in southwest Austin is “undetermined,” though most likely a child in the home ignited a blanket.

The fire occurred at about 7:30 a.m. in a second story bedroom at 405 Third Ave. S.W., injuring one person.

Symone Khalek suffered blisters to her hands, feet and arm after pulling the burning blanket off a bed, Wilson said.

She was taken to Austin Medical Center, where she was in fair condition Wednesday.

Wilson also said Thursday that the fire could have been fatal for people upstairs had they remained in the house for several more minutes, due to toxic fumes from a burning mattress.

Six people were home at the time, including three children. A 7-year-old boy had left for school before the fire.

Wilson said the family was “lucky” because there were no smoke detectors on the second floor; the first floor had a detector, but it did not have a battery.