Child, Youth and Family (CYF) says demand is increasing as the courts remand more young people into its care or sentence them to serve a supervision with residence order.
A national shortage of youth justice beds meant eight young people had to spend the night in police cells across the country on a recent Sunday.
Another young person was being monitored in the community while waiting for a youth justice bed and another was undergoing a mental health assessment in a hospital.
In Dunedin, a 16-year-old spent a night last week in a Dunedin Central police station cell because no beds were available in secure youth facilities.
He was bailed the following day to the community, where he is being monitored until one of 116 beds at CYF's youth justice facilities in Christchurch, Palmerston North, and Auckland, comes free.
CYF residential services operational manager Mark Painter said more youths were being remanded into CYF care or sentenced to serve a supervision with residence order.
Under the order, a young person is detained for a period of up to three months, but that will become six months when new legislation comes into force later this year.
Dunedin police say they held two youth justice clients overnight in the first two weeks of August.
The issue had at times been worse, but it was not ideal for any young offender to be kept in police cells, particularly as they had to be kept separate from other offenders, Dunedin-Clutha area commander Inspector Dave Campbell said.
In Dunedin, young offenders were held in the women's cell, precluding the police from arresting women while they were there, he said.
There is a three-bed secure wing at the CYF care-and-protection residence, Puketai, in Andersons Bay, but it is not available for young offenders on residential orders or remand because of a national CYF policy to keep care and protection campuses and youth offenders apart.
Rolleston, near Christchurch, has the South Island's only youth justice facility.
Mr Painter said he hoped any waiting-list issues would be resolved when a new 30-bed youth justice facility in Rotorua became operational at the end of this month.
Dunedin youth advocate Brian Kilkelly thought it was probably true that the courts were placing more young people into CYF custody and sentencing people to a stay in a residential facility.
He understood the trend was that fewer people were appearing in Youth Court, but the offences were more serious - which would also translate into more people being sentenced to serve supervision with residence orders.
Anecdotally, he was aware lawyers were seeing a lot more knife crime, aggravated robbery and general "street thuggery" from youth offenders.
There was always a squeeze on youth justice beds, but he had not detected any growing problem with availability, which was something he and his colleagues would "certainly" be vocal about if it were a concern.
However, he expected this year's law change, making possible supervision with residence orders for six months, would put extra strain on youth justice beds.
