Cassandra Brown-Crane's two-year-old son Alijah returned to the Yass Little Learners childcare centre on Thursday, after he was left on the centre's bus on Wednesday.

Ms Brown-Crane wrote on social media on Thursday that it was a complete accident that her son was left on the bus and while she didn't blame the centre she was not happy that it had happened.

Ms Brown-Crane wrote that the childcare centre staff were not to blame.

"I feel that it needs to be said the school he attends is a wonderful centre," she said.

"Accidents do happen. Sadly, this could have been tragic, but thankfully he's healthy and happy," Ms Brown-Crane told The Yass Tribune.

"I'm relieved it didn't end up fatal," she said.

"I'll remember this day forever and I'm so thankful he his healthy and alive. He bounced back very fast."

Ms Brown-Crane said she had counted her blessings every second since she was called.

"Hold your babies close tonight, I know I will," she wrote on Facebook on Wednesday.

NSW Police are investigating after the child, who was collected from home by the childcare's bus service, was left in a vehicle on a 28-degree day, strapped into a child's restraining seat.

Officers and paramedics attended the scene at about 3pm on Wednesday. The boy was removed from the restraint and treated for dehydration, before being taken to Yass Hospital for monitoring.

He was discharged from the hospital at 6pm.

No charges have been laid and the Yass Little Learners childcare centre is assisting with inquiries, a NSW police spokesman said on Thursday.

Another local parent, who asked to remain anonymous, told The Yass Tribune her son was also left on the childcare's bus service in 2017. Staff were only alerted to the alleged mistake after an older public school student, who was getting off another bus, noticed the boy in distress.

A complaint was later made with the Australian Children's Education and Care Quality Authority, the parent said.

Police confirmed the alleged incident is part of their ongoing investigation into the childcare centre's bus service.

A local father, who also asked to remain anonymous, told The Yass Tribune he saw a teacher with a clipboard checking off children who were leaving the centre when he collected his son on Wednesday.

"Until we understand why they didn't have processes in place to pick this up, then we can't really let [our son go back to the centre]," he said.

On social media, several other parents whose children attend the centre said they would also look for alternative day care because of the incident.

Mitchell Ballard told The Yass Tribune the child care centre was quiet when his partner dropped off their son on Thursday morning.

The centre told parents the bus driver had been suspended and the incident would be investigated.

"The centre and management takes this opportunity of assuring parents that every effort is being taken to ensure that a full enquiry is conducted."

The co-owner of the Little Learners Group, Steve Grundy, told The Yass Tribune that the centre was pleased the child was in good health.

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

Mr Grundy told WIN News on Thursday that the centre was sorry the incident had occurred.

"Anything with children is very, very emotional and children, we’re here to protect," he said.

"We’re very, very sorry. We’re very much wanting to help as much as we can."

The matter has been reported to Family and Community Services and police will share findings from their investigation with the department.

The childcare centre posted on its website in April 2017 to about the then-new bus service, which was able to collect children from the town and nearby Murrumbateman.

with Emily Barton