SIOUX FALLS, S.D. (AP) - Investigators say they should be able to pinpoint the cause of a house fire in Sioux Falls last month that killed three children.

Authorities got their first look inside the burned-out home Tuesday. Sioux Falls Fire Rescue investigator John Daniels tells the Argus Leader newspaper that the fire's origin and cause might be determined in as little as a week.

KELO-TV reports that an accelerant-sniffing dog was brought in for a second time to search for any evidence of gasoline or other fuel, and again did not find anything.

The fire early on Dec. 22 killed 16-year-old Michael Hensley, 12-year-old Savannah Coon and 6-year-old Alivia Coon. Their mother, Rhiannon White, appeared in court on drug charges on Wednesday and was assigned a court-appointed attorney, who asked for a preliminary hearing.