Guojun Xuan, 65, and his partner, Silvia Zhang, 38, were arrested in May on suspicion of child abuse after their 2-month-old son suffered traumatic head injuries, NBC News reported. They were released on bond while investigators continue examining the case.

Police say video evidence shows children in the couple’s care enduring physical and emotional abuse by caregivers, which Xuan and Zhang allegedly allowed to happen. One video reportedly depicts a 56-year-old nanny violently shaking and striking the infant.

Investigators discovered 15 children living in the couple’s nine-bedroom home, with six more staying with friends, totaling 21 children between 2 months and 13 years old. All have been placed in foster care. Officials have not determined how many were born through surrogacy. The couple reportedly has one child together, and Xuan is believed to be the father of a 13-year-old daughter.

Several surrogate mothers claim they were misled about the couple’s intentions and family situation. They allege that Xuan and Zhang controlled the surrogacy agency representing them, and some were unaware that federal authorities were investigating potential child trafficking.

Two surrogate mothers, Kayla Elliott and Tronderrica James, are seeking custody of children they carried for the couple. James described the couple’s behavior as “foul, reckless, and cruel,” alleging she was misinformed about their family status and intentions.

Xuan and Zhang have filed lawsuits against at least two surrogates who ceased contact before delivery, citing breach of contract. The couple denies any wrongdoing, maintaining they only sought to have a large family.

The FBI declined to comment, and no additional criminal charges have been filed. Reports indicate that five more children have been born to surrogate mothers connected to the couple in the last six months, adding complexity to the ongoing investigation.

Representatives for Xuan, Zhang, and the Arcadia Police Department did not respond to requests for comment.