An eight-year-old boy rushed to hospital in a critical condition had hid himself in the back of his mother’s van in Melbourne and spent several hours inside the vehicle before he was found.

The youngster was found “unresponsive” by his mother about 2.45pm on Monday as the temperature soared to more than 30C.

“The boy’s mother dropped her children at primary school in the morning, however, didn’t realise one of the kids had climbed into the rear of the car and hid himself,” said Victoria Police spokeswoman Leonie Johnson.

“She has driven to work and parked her car without knowing he was in there.”

After she made the shocking discovery, emergency services rushed to Maddox Road at suburban Newport and took the child to the Royal Children’s Hospital, which late on Tuesday afternoon confirmed his condition had improved to serious.

Police initially called in the homicide squad, but have since confirmed they are treating the incident as an accident.

The principal of Newport Gardens Primary School where the woman worked released a statement to parents and carers on Monday.

“As you may be aware, an incident occurred today at school involving a staff member and a member of their family,” principal Simon McGlade said in the statement.

“The incident didn’t involve any students from our school,” he said.

Footage from the scene showed police examining a black people mover, parked in the street, which was later removed.

Victoria’s Health Minister Jill Hennessy offered a general warning to parents on Tuesday.

“Get your children out of the car, do not leave them there, whatever inconvenience that involves, it’s a price worth paying,” she said.

“It can be really inconvenient to get them in and out of baby seats, parents are really busy, but a child left in a car can easily die.”

The school sent well wishes to the family involved.

“Support will be made available for any staff, students and families that need it,” Mr McGlade said, asking for privacy for those involved.

-AAP