Detection dogs were brought into Auckland's Ronald McDonald House on Wednesday after staff became suspicious someone had brought drugs in.
The sweep was announced in a letter sent out to families staying at the Auckland house on Wednesday, telling families that "unfortunately is has been necessary to bring the drug detector dogs through the house today".
"We treat the breaking of any house rules very seriously, as these rules are in place to ensure the safety of all families and their comfort while staying at Ronald McDonald House," the letter read.
The houses in Auckland, Wellington and Christchurch are a home away from home for sick children and their whanau during hospital treatment.
When asked by the Weekend Herald, a spokeswoman said there had been some suspicion someone had drugs on the property but she would not be drawn on what specifically caused staff to bring detector dogs in.