A search is underway in bushland north-west of Sydney for a newborn baby suspected of being murdered up to a decade ago.

The NSW Homicide Squad received information earlier this year that the baby was murdered not long after being born in late 2007 or 2008.

It is understood the baby's mother was in her late teens when she gave birth.

The infant wasn't alive for long, possibly only a matter of days, before police believe it was killed and buried on a rural property on the north-western fringes of Sydney.