Elisa Baker made the emergency call at 5 a.m. Oct. 9, saying piles of wood and mulch at her Catawba County home were burning, The Charlotte Observer reported. She did not mention 10-year-old Zahra Baker.
Adam Baker called 911 seven hours later to say he could not find the girl.
Elisa Baker, 42, is in custody on a charge of obstruction of justice and is scheduled for a bail hearing Wednesday. Investigators say she admitted writing a note demanding ransom, which they believe was a cover aimed at throwing police off track.
Zahra is partially deaf and missing part of one leg from bone cancer. CNN reported Monday police are seeking her medical records in Australia where she lived until her father met her stepmother online.
Firefighters discovered the ransom note tucked under a windshield wiper of a vehicle at the Baker home. The note demanded $1 million from Mark Coffey, Adam Baker's boss at a tree maintenance company, suggesting a Coffey daughter had been kidnapped.