A California woman was arrested Monday after authorities found her 3-year-old son tied up inside a burning home with a plastic bag over his head, authorities said.

Firefighters in the Southern California city of Santa Paula also found the woman, Maricela Magana Ruiz, 47, bound in her bedroom, police said in a statement.

Maricela Magana Ruiz. Santa Paula Police

Magana Ruiz was booked early Monday on suspicion of child endangerment after she allegedly tied the boy up in his bedroom and put the bag over his head, the statement and jail records say.

The cause of the fire remained under investigation, Detective Sergeant Allen Macias told NBC News. He said it wasn’t clear why or how Magana Ruiz had been tied up.

Both had been bound — Magana Ruiz at her feet, the boy at his hands — with "something similar to shoe string," Macias said.

The department said authorities were called to the home in Ventura County, north of Los Angeles, after a 911 report of a structure fire on Sunday night shortly after 6 p.m local time.

Firefighters extinguished the blaze and Magana Ruiz and her son were treated for smoke inhalation at a local hospital.

It wasn’t immediately clear if Magana Ruiz has a lawyer. Jail records didn’t list one.

An official with the Ventura County Jail said Magana Ruiz had been released on $50,000 bail.