PERRIS, Calif. -- From the outside, the brown-and-beige four-bedroom home looked fairly orderly. Inside, it was a veritable torture chamber for 13 siblings who lived with their parents, police said.

The couple who owned the home purchased it new in 2014 and soon arrived in the rapidly growing city 70 miles (113 kilometres) southeast of Los Angeles with their 12 children. They lived there quietly for at least three years and had another baby.

Then, on Sunday, one of the children jumped out of a window, called 911 and led authorities to the home and the bizarre scene inside.

Sheriff's deputies said they found the couple's 13 children ranging in age from 2 to 29 years old, some of them chained to furniture, all of them thin and malnourished. The 17-year-old girl who escaped was so tiny that deputies initially mistook her for a 10-year-old.

Riverside County Sheriff's Capt. Greg Fellows said the 911 call came from a cellphone that had been deactivated but still worked for emergency calls.

When deputies found the girl he said she showed them family photos that prompted them to visit the house. Authorities confronted the girl's mother, Louise Anna Turpin, and Fellows said she appeared "perplexed" as to why they had come.

Turpin, 49, and her husband, David Allen Turpin, 57, were jailed on $9 million bail. They were scheduled for an initial court appearance on Thursday. Authorities said the pair could face charges of torture and child endangerment.

"If you can imagine being 17 years old and appearing to be a 10-year-old, being chained to a bed, being malnourished and injuries associated with that, I would call that torture," Fellows said.

He said there was no indication any of the children were sexually abused, although that was still being investigated.

Neither sheriff's deputies nor child welfare officials received a single call over the years about the Turpin home, he said.

The investigation, still in its early stages, has already begun to unravel a surreal tale of a couple married 32 years who sometimes dressed their children alike, kept them away from outsiders and cut the boys' hair in a Prince Valiant-style resembling that of their greying father. Photos show nearly all the girls with shoulder-length brown hair parted in the middle.

Videos posted on YouTube show the couple renewed their vows at the Elvis Chapel in Las Vegas at least three times in recent years, most recently on Halloween 2015. An Elvis impersonator dressed in a glittering jacket performed the ceremony between songs. Most of the children, dressed in matching outfits, took part.

"It's very disturbing because I felt like I did know them," the Elvis impersonator, Kent Ripley, told The Associated Press on Tuesday. "I was surprised and shocked and stunned that this could even have been happening."

He recalled the children looked very thin but said he chalked that up to their lifestyle.

"It didn't stand out that it would be a physical abuse or lack of feeding," Ripley said.

Numerous photos on the couple's Facebook page show the children dancing at the Elvis Chapel, visiting an amusement park that appears to be Disneyland and going on other outings, always looking thin but often smiling.

Although their home appeared nondescript from the outside, it was a stinking mess inside, Fellows said. He called the conditions "horrific."

State Department of Education records show the home's address is the same as the Sandcastle Day School, where David Turpin is listed as principal. In the 2016-17 school year it had an enrolment of six. Fellows told reporters there is no indication any student other than the couple's children were enrolled there.

No state agency regulates or oversees private schools in California, and they are not licensed by the state Education Department. Private school operators are required to file an affidavit with the state annually, listing the number of students, staff members and information about the school's administrators.

Private schools are also subject to an annual fire inspection.

Representatives for the state Department of Forestry and Fire Protection and the Riverside County Fire Department would not immediately say whether the Turpins' home was inspected.

Mark Uffer, CEO at Corona Regional Medical Center, said seven of the couple's children were there Tuesday.

"I can tell you that they're very friendly. They're very co-operative, and I believe that they're hopeful that life will get better for them after this event," he said.

Before moving to Perris, a city of 76,000, the family lived for a time in nearby Murrieta. Property records show they moved to Southern California in 2011 from the Dallas area.

The Turpins filed for bankruptcy that same year, stating in court documents that they owed between $100,000 and $500,000. At that time, Turpin worked as an engineer at the Northrop Grumman aerospace company and earned $140,000 annually and his wife was a homemaker, records showed.

Neighbour Kimberly Milligan said the developer who built the tract where they lived told her the family had a dozen kids when they moved in, although she never saw that many.

She described the family as "standoffish" hoarders who had their garage filled with books and who often let the grass in their front yard grow out of control, unlike other families on the block.

"I got an impression, that, you know, 'You stay in your lane, I'll stay in my lane," she said. "It was never, 'Hi.' Never a wave. Nothing."

Her 26-year-old son, Robert Perkins, said he only remembers seeing four children outside the home, recalling they all appeared pale and skinny, as if they never ventured outside.

Dr. Donald Kirby, director of the Center for Human Nutrition at Ohio's Cleveland Clinic, said those pale complexions could reflect not only lack of sunshine but also iron deficiencies caused by insufficient vitamins.

He said the youngsters' small stature and childlike appearance also indicates they were likely undernourished for many years.

"What that means is this has been a very long process and that during the real growth spurt years that the needed nutrients weren't given," Kirby said. "At some point the body locks in and you're not able to grow anymore. This didn't happen last week, last month or even last year. This has been going on probably a very long time."

He said their recovery period, both physically and emotionally, will likely be long and arduous.

"Lots of things are going to need to be done for these poor people," he said. "Hopefully they get the care they need to try to reverse as much as can be reversed and that they are allowed to develop normal lives. It'll be quite a challenge."