Superintendent John Quilter confirmed a garda probe is under way after footage of the incident was posted on social media.
It has since gone viral.
The 19-second clip, recorded on a mobile phone by a concerned citizen, shows the infant sitting alone in a car, strapped into a rear-facing child seat, in the car park of the Market Green Shopping Centre in Midleton at lunchtime on Tuesday. The child appears to be playing happily with a mobile dangling from its car seat handle.
A rear window on the other side of the car, and the driver’s window, were both left open a few inches. Temperatures hit 20C at the time.
It was claimed that a couple had left the infant in the car for up to 20 minutes while they visited a shop with an older child, although it’s understood the baby was left unattended in the car for a much shorter period.
Gardaí were alerted and the woman who recorded the footage challenged the couple when they returned.
Supt Quilter said gardaí are treating as serious the fact the infant was left unattended. He said gardaí will also liaise with the child and family agency Tusla.
Their probe will involve interviewing witnesses, examining mobile phone footage, and the harvesting of CCTV footage from the area to establish an exact timeline of events, including the length of time between when the couple left the infant and when they returned.