ARCADIA, Calif. — A California couple’s 21 children – all from surrogate mothers – have been placed in protective custody amid an investigation.

Arcadia police stumbled upon a house on Camino Real Avenue while investigating a child abuse case involving a 2-month-old suffering a traumatic head injury.

After getting a search warrant, detectives seized security cameras from inside the home and made some alarming discoveries.

“We discovered numerous children – 15 children to be specific – ranging in ages from 2 months old to 13 years old,” Arcadia police Lt. Kollin Cieadlo said.

“Many of the children were birthed through surrogacy and then the male and female at the residence took legal guardianship of those kids,” Cieadlo added.

Six other children, investigators say, had been moved to other homes. All 21 of the kids were confirmed to be the children of 65-year-old Guojun Xuan and 38-year-old Silvia Zhang. They were arrested for felony child endangerment but later released.

Police have also issued an arrest warrant for their nanny, 56-year-old Chunmei Li. Investigators say after looking at surveillance video, she is the main suspect in the child abuse case and is still on the loose.

“The discipline, both verbally and physical, was severe to the point where it supported the beliefs that child abuse was occurring inside the home,” Cieadlo said.

Sources told ABC Los Angeles affiliate KABC that of the 21 children, 17 are 3 years old or younger. Police say all 21 children are in the custody of Department of Children and Family Services.

Where did all those children come from? That is what the FBI is trying to figure out. The bureau refused to comment on the case, but Arcadia police confirmed that their detectives are working with the FBI.

Arcadia’s investigation, though, determined that the children are the product of a surrogacy operation owned by Zhang and Xuan.

No charges have been filed. The Los Angeles County District Attorney’s Office is not commenting on the case.

“It’s horrific, it’s disturbing, it’s damaging emotionally,” said Kayla Elliot, one of the surrogate mothers hired by Zhang and Xuan.

She says they told her they only had one other child. She’s now hoping to get custody of the child that she had for the couple.

“These agencies, we’re supposed to trust them and follow their guidance and come to find out this whole thing was a scam, and the parents own the agency – that was not disclosed at all beforehand,” Elliot said.

“Anything goes. And these clinics, these agencies are not regulated by any governing body,” said Kallie Fell, executive director of the nonprofit Center of Bioethics and Culture.

Fell is working with Elliot. She says having more than 20 children through surrogates is not illegal, but that it raises serious questions as to why people would do that.

“That to me smells of trafficking, child trafficking,” Fell said. “What are the intentions of having that many children at home through these assisted reproductive technologies?”