"She wasn't particularly co-operative so we have to go with what's in front of us," he said. "Given her state you would expect it would be a reasonably fresh binge session, but who knows."
The woman was taken to the Hastings Police Station where she was processed for drink-driving. She will appear in Hastings District Court on Wednesday, charged with dangerous driving and refusing to give a blood sample.
The school-aged child went to school as normal on Wednesday, while the pre-schooler was taken to a family friend's house.
"Police had to go back to the station and get a car seat because the toddler was completely unrestrained," Mr Brown said.
"Luckily, there was a family friend who lived nearby who could look after the toddler."
Mr Brown said police had spoken to all relevant witnesses and had sufficient evidence to take the matter to court.
There would be no further charges at this stage.
The school had not been involved in the police investigation as the incident happened outside school grounds, Mr Brown said.
Senior Constable Andy Clinton said the incident, which had left officers dumbfounded and angry, was particularly disturbing in light of recent publicity for Road Safety Week this week.
Checkpoints had been set up outside some schools and arterial routes, with police checking on seatbelt wearing, cellphone use and enforcing the 20km/h speed limit past stationary school buses.
Ministry of Social Development spokeswoman Amanda Forsey said Child, Youth and Family would not comment on its involvement in the case as it was a police matter.