Los Angeles - A California couple arrested on suspicion of torture was due in court on Thursday after investigators discovered they were holding their 13 malnourished children captive in a suburban home.
David Allen Turpin, 57, and his wife Louise Anna Turpin, 49, had registered their home as a school, but instead of teaching materials, investigators found signs of torture inside.
County officials investigating the case announced a press conference for 1500 GMT Thursday. The court was expected to announce charges a few hours later.
Read more: 'Very normal' US parents charged with torture of 13 children
Sheriff's deputies in Perris, a town southeast of Los Angeles, found three children shackled with chains and padlocks in their filthy, foul-smelling home Sunday after receiving an emergency assistance call from their 17-year-old sister who had managed to escape.
She was so emaciated that officers first thought she was a young child.
Officers also initially assumed all the other siblings to be children, but were shocked to discover seven ranging in age from 18 to 29.
All 13 are being treated for malnutrition and undergoing other diagnostic tests.
Mark Uffer, chief executive officer at the Corona regional medical center where the adults were being treated, described their condition as stable.
David and Louise Turpin were booked on suspicion of torture and child endangerment with bail set at $9 million (about R111 million) each.
- No indication of abuse -
Neither was able to immediately explain why their children were restrained, according to the Riverside County Sheriff's Department.
Police said there was no initial indication of sexual abuse, but cautioned that the investigation was still going on.
Nor was there any indication that either suspect suffered from mental illness, Perris police chief Greg Fellows said, or that the children's ordeal was linked to the family's religious beliefs.
Initial investigations have confirmed that the couple were the biological parents of all 13 siblings, Fellows said.
According to police, the family moved in 2014 from Texas to a middle class neighborhood of Perris, some 70 miles (110 kilometers) southeast of Los Angeles, homeschooling their children in their Spanish-style stucco house.
A sister of Louise Turpin, Elizabeth Flores, told ABC the couple kept to themselves.
Also read: 'Tortured' Californian siblings set for a long, hard road to recovery
"This has been going on before they even had children ... they were real private, and they didn't come around much," said Flores. "We begged to Skype them. We begged to see them."
As a university student Flores lived with the Turpins for a while.
"I thought they were really strict, but I didn't see any abuse," Flores said.
But she said she did have disturbing memories of the husband. "If I went to get in the shower, he would come in while I was in there and watch me. It was like a joke. He never touched me or anything."
The case recalls previous kidnapping horrors that have made global headlines in recent years.
Ariel Castro abducted three young women he repeatedly raped for a decade at his Cleveland home. He was arrested in May 2013 after one of his victims escaped.
Jaycee Dugard was kidnapped as an 11-year-old and repeatedly raped over 18 years by convicted sex offender Phillip Garrido in California. She was rescued in August 2009.
Austria has seen two high profile kidnaps -- Elisabeth Fritzl was imprisoned and raped over a period of 24 years by her father Josef while Natascha Kampusch was held for eight years by Wolfgang Priklopil before her 2006 escape.