City officials couldn't find any records that the fire marshal conducted required annual inspections at a California home that doubled as a private school where authorities say 13 malnourished siblings were kept captive in filthy conditions by their parents.

On Wednesday, a state lawmaker for the area said he's considering introducing legislation requiring state officials to conduct at least annual walkthroughs of schools.

Private schools in California are not licensed by the state education department and no agency regulates or oversees them, although they are supposed to register the number of students. They are, however, subject to an annual inspection by the state or local fire marshal.

"I am extremely concerned about the lack of oversight the state of California currently has in monitoring private and home schools," said Assemblyman Jose Medina, a Democrat who represents the area.

In response to a public records request by The Associated Press, Perris assistant city clerk Judy Haughney said Wednesday that there were no records of any fire inspections conducted at the home. The city's fire marshal, Dave Martinez, did not return repeated phone messages seeking comment.

David Allen Turpin and his wife, Louise Anna Turpin, were arrested Sunday after authorities found the malnourished children in their home in Riverside County. The couple was jailed on $9 million US bail each. Charges that may include torture and child endangerment could come Wednesday and a court appearance was scheduled for Thursday, authorities said.

Parents charged with torturing their children1:57

Deputies said some siblings were shackled to furniture in the foul-smelling home in suburban Riverside County. They were so malnourished that the older ones still looked like children.

David Turpin had been home schooling his children at the residence, which he called the Sandcastle Day School. In the 2016-17 school year, it had an enrolment of six, with one student each in the fifth, sixth, eighth, ninth, 10th and 12th grades.

More than 3,000 private schools were registered with the California education department in September 2017, according to the latest data available.

Laws vary across the U.S. for homeschooling children. Some states require very little oversight, while California's requirement of registering children is one of the most stringent.

The 2015 killing of a seven-year-old Kansas boy who was supposedly being home schooled prompted calls for reform in that state, though none have gone through. Kansas similarly requires schools to register and directs them to provide "competent" teachers but has no other oversight.

Shackled Children

Members of the media work outside the Turpin's home on Tuesday in Perris. City officials couldn't find any records that the fire marshal conducted required annual inspections at the home that doubled as a private school. (Alex Gallardo/Associated Press)

State Sen. Richard Roth, a Democrat who also represents Perris, said it's critical to make sure laws on the books, such as the one requiring fire inspections of private schools, are enforced.

"We need to make sure people are following the laws and regulations we do have," he said.

Ron Reynolds, the executive director of the California Association of Private School Organizations, which represents 1,500 private schools, said most schools are regulated by boards of directors and parents, who sign contracts and review standards before enrolling their children.

Police search home

Investigators on Wednesday conducted an exhaustive search of the foul-smelling, filthy tract home, police said.

"We have investigators on scene, combing through everything they can find for additional evidence," Riverside Sheriff's Deputy Mike Vasquez told Reuters. "They're trying to gather more information that may assist them in providing a full description of what was going on there.

"The whole house is a crime scene," he added.

Shackled Children

Louise Turpin and David Turpin as they appear in booking photos provided by the Riverside County Sheriff's Department in California. (Riverside County Sheriff's Department/Associated Press)

On Wednesday afternoon, several investigators, some wearing black gloves, went in and out of the house, frequently carrying boxes and bags of material they placed in waiting vehicles.

Inside the garage, floor-to-ceiling shelves that appeared to be stacked with DVDs could be seen.

Concerning signs

From the outside, the tan house did not look particularly different from the one-and two-storey houses in the community. But neighbours said the thick sod of the front lawn had been put down by the children last fall, working at night under TV-style lights as their mother looked on.

On Wednesday, police and prosecutors prepared for the arraignment of each parent on nine counts of torture and 10 counts of child endangerment.

Elizabeth Jane Flores

Author Elizabeth Jane Flores, Louise Turpin's sister, told ABC News that in hindsight, there were concerning signs, including a refusal to allow family visits or talks with the children on Skype. (Facebook)

Neighbours and family members have offered little insight into the couple's motivations or actions. Experts have said it may have been easier for the parents to shield their children from scrutiny because they were home-schooled.

Reached by telephone Wednesday at the West Virginia home of David Turpin's parents, his mother, Betty Turpin, said she was busy preparing paperwork and entering information into a computer to help her son. She said the family had engaged an attorney, who advised them not to speak about the case.

But Louise Turpin's sister, author Elizabeth Jane Flores, told ABC News on Wednesday that in hindsight, there were concerning signs, including a refusal to allow family visits or talks with the children on Skype.

With files from Reuters and CBC News