Child, Youth and Family (CYF) believe a Tuakau brother and sister who had gone missing from their caregiver's house are being used as "bargaining chips" in a custody battle.
Anahera McLean, 7, and her brother Te Morehu left the home late at night on July 18 with a large suitcase, sparking a major search for them.
At the time, police say the pair had likely left the house of their own accord and their disappearance wasn't as a result of an argument.
The pair were eventually found safe, with the mother telling CYF they are with the wider family.
However, CYF says they're concerned the mother won't tell them or police where they are "so we can be satisfied about their safety".
In a statement, CYF accused the family of using the children as "bargaining chips" in a custody wrangle.
"Decisions around the custody of children and young people are a matter for the Family Court and are made with the best interests of the children as an absolute priority. No decisions can be made while these children are still missing."
They've pleaded with the McLean family to "bring the children out of hiding".