Four children were treated for carbon monoxide inhalation after their school bus was evacuated near Swaffham this morning (Monday).
Paramedics and fire crews from King's Lynn, Downham Market and Swaffham were called when pupils smelled exhaust fumes on the bus.
Ambulance crews treated the children at the scene and two were later taken to the Queen Elizabeth Hospital in Lynn.
An ambulance service spokesman said the children were alert, but having difficulty breathing.
The bus pulled over in Chalk Lane at Beachamwell at 8.45am.
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