The boy was riding a tricycle on Montgomery St, Hastings, when struck by a vehicle head-on.
Sergeant Ray Kirkby said witnesses described the vehicle as black with a silver stripe. It left the scene in a northerly direction, heading towards Gascoigne St, about 3pm.
"We are continuing our inquiries at this point and hoping members of the public will come forward" Mr Kirkby said yesterday when contacted by Hawke's Bay Today.
One neighbour said he heard a "loud bang" and rushed outside to see what had happened.
"I came out to the road and the boy was lying on the ground, bleeding, just lying there on the side of the road. The car just went straight over him," the man said.
Neighbours said the street was always filled with kids playing.
"He would have seen him [the boy] coming up the road, there is no way he wouldn't have seen him," said one neighbour.
A Hawke's Bay Hospital spokesperson said the boy, who had lower abdominal injuries, was in hospital overnight Sunday in a stable condition but was discharged yesterday.