Police are investigating and Oranga Tamariki have been called over the injury to the boy.
An Auckland mother has denied hospital staff accusations of breaking her one-month-old son's arm.
Police are investigating and Oranga Tamariki has been informed about the injury to the boy.
The child was admitted to Middlemore Hospital on January 23 with a case of suspected measles.
While doctors soon determined it was a common hormonal rash, they spotted a bruise on the baby's arm.
An X-ray confirmed that it was broken.
The boy's mother says hospital staff have accused her of being an "inattentive mother" and would not let them go home together, according to the woman's father.
"God knows how a doctor can make that kind of assessment after seeing a child for 10 minutes," he told the Herald.
"From my point of view, I can't say it was the hospital or an accident happened. But as much as they are pouring blame at her, they should be up for investigation as well because there is a likelihood it happened at the hospital."
The family says they have a photograph taken at the hospital which "clearly" shows the boy's bare arm with no bruising.
They say an independent radiologist concluded that the break must have happened in the 24 hours prior as it had not yet begun to heal.
Police say they are investigating following a report of a child having been injured "prior to them presenting at hospital" last Wednesday.
Oranga Tamariki said they couldn't comment on individual cases without a signed privacy waiver, as did Counties DHB.
A spokeswoman said the health and safety of patients is "of utmost importance".
"In the case of children, we have standard processes in place to ensure their safety and we follow these processes at all times," she added.
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