As authorities continue to search for missing Texas toddler Sherin Mathews, the 3-year-old’s parents have ceased cooperating with police. Sherin’s parents are, however, working to regain custody of their other child.

Sherin went missing October 7 after her father reportedly left her outside in the middle of the night as punishment for not drinking her milk. Wesley Mathews told police when he returned to fetch his daughter at about 3:15 a.m., she was gone. Mathews waited five hours to call police, during which time he allegedly conducted a short search for Sherin before returning home to do a load of laundry. Authorities also discovered the family car went missing for about an hour at 4 a.m. after Sherin disappeared.

Mathews was arrested for endangering a child after Sherin went missing, but was released on bond. Sherin’s mother was reportedly sleeping throughout the night Sherin disappeared. The Mathews adopted Sherin two years ago from an orphanage in India. She has limited communication skills and developmental issues.

In the wake of Sherin’s disappearance, Child Protective Services intervened to remove the Mathews’ 4-year-old biological daughter from the home. CPS said they had prior contact with the Mathews family before Sherin vanished, but provided no further details. The girls’ mother, Sini Mathews, was scheduled to attend a hearing Monday in an attempt to regain custody of her biological daughter, KVTV reported.

Both parents have retained lawyers, despite the fact that Sini Mathews has not been accused of any wrongdoing.

“They adopted Sherin, they love Sherin,” said Sini’s lawyer, Kent Starr, according to the Dallas Morning News. “[Sherin’s mother] does not know the whereabouts and all she wants is for her daughter to be returned.”

The parents have come under fire from some people in the community for their responses to Sherin’s disappearance. Neither the mother or father appeared at a vigil held for the girl. When asked by reporters why Sini has not spoken publicly about her daughter’s disappearance or made a plea for her return, Starr said people react to situations differently.

“The mere fact that you do not hear from a person who is mourning – some individuals mourn differently,” Starr said, noting that Sini hoped her daughter would be found. “The fact that she may walk up and down the street and react differently to a time of trauma is not indicative of anything.”

Authorities and volunteers have continued to search for any trace of the little girl in and around Richardson. FBI agents seized numerous items from the Mathews home during a six-hour search, while local police said a search in a nearby area yielded “articles of interest.”

“The longer a person is missing, the more critical it is to find them,” said Richardson Police Sgt. Kevin Perlich. “As time goes on, it becomes less and less likely you are going to have a good conclusion to it.”