Officers confirmed they and paramedics were called to 116 Rossi Street, the Yass Little Learners (YLL) child care centre, just after 3pm on February 20.

Officers said the toddler had been left in the vehicle unattended for about six hours. The top temperature in Yass had reached 28 degrees Celsius.

The two-year-old boy was removed from a child restraint seat inside the bus and treated at the scene for dehydration before he was taken to Yass Hospital, where he was kept for observation until 5pm.

In a statement to parents via Facebook, Yass Little Learners confirmed the incident took place on its bus. The driver was "suspended pending a full investigation by YLL centre management," the statement read.

The statement, released about 9pm, went on to assure parents that "every effort is being taken to ensure that a full inquiry is conducted … We will provide a further report of the results of this matter."

But a local parent who asked for anonymity told the Yass Tribune their son had also been neglected in the summer heat on a Yass Little Learners bus two years ago, during his kindergarten year.

A school child who had alighted from a public school bus had alerted staff to his distress; and a complaint was later lodged with ACECQA (the Australian Children's Education and Care Quality Authority), the parent said.

Yass Little Learners director Steve Grundy said the child care centre was "very pleased the child is in good health".

"The health and well-being of the child was paramount. We contacted paramedics and police straight away and full inquiries are now being undertaken," Mr Grundy said.

Mr Grundy would not comment as to whether this kind of incident had happened before, stating that as the current situation was under investigation, he couldn't say much.

According to the Yass Little Learners' website, the child care business is planning to open centres in Mudgee, Lake Cathie and Bruce in Canberra.

On Thursday morning, Mitchell Ballard's partner dropped their son to Yass Little Learners and said it was very quiet. 

Another parent, Mel, chose to take leave from work and stay with her two children, to find an alternative day care centre. "I just can't send them back after this," she said.

Mel's oldest daughter has travelled on the YLL bus for outings. "It makes me feel sick to think this could have been one of my girls."

Hume Police will report their findings on the February 20 incident to Family and Community Services (FACS).

More to come.