California authorities have placed 21 children in protective custody after discovering that all were born to surrogate mothers hired by a couple living in Arcadia, about 13 miles northeast of downtown Los Angeles. The children, ranging in age from two months to 13 years and including 17 toddlers, were removed from a $4.1 million residence and from other locations following a child-abuse inquiry. Police identified the legal parents as Guojun Xuan, 65, and his partner Silvia Zhang, 38. The investigation began in May when a hospital reported a two-month-old infant with a traumatic head injury. Xuan and Zhang were arrested on suspicion of felony child endangerment and later released. Fifteen children were found inside the home; six more were located with relatives or friends. All 21 are now in the care of the Los Angeles County Department of Children and Family Services. Detectives say security-camera footage from inside the house shows emotional and physical abuse by at least one caregiver. An arrest warrant has been issued for the couple’s nanny, 56-year-old Chunmei Li, who remains at large. Arcadia police are working with the FBI to determine whether the surrogacy arrangement constitutes human-trafficking or other criminal conduct. Business records list the couple as operators of Mark Surrogacy Investment LLC, recently renamed Future Spring Surrogacy, which was registered at the Arcadia address. Several surrogate mothers across the United States told investigators they were led to believe the couple wanted only one additional child. While having multiple children through surrogacy is not illegal, experts say the case highlights the lack of federal oversight of commercial surrogacy and raises questions about the purpose of assembling such a large group of very young children. No additional charges have been filed as the probe continues.