Police and the Ministry of Business, Innovation and Employment (MBIE) are investigating what caused a bobcat digger to fall down a hill on a property near Poraiti, Napier, yesterday afternoon.
Hawke's Bay police sergeant Clint Adamson said the bobcat appeared to have become stuck on an incline and a heavier digger attempted to move it on to level ground.
"But for some reason we are yet to determine, it has come free and tumbled down a steep incline with the driver of the bobcat still inside. The [23-year-old] driver has suffered some reasonably serious injuries and has been taken to [Hawke's Bay] hospital in Hastings," he said.
A staffer from the MBIE was also at the scene last night.
The driver of the second digger provided aid until emergency services arrived but had left the scene by the time police arrived.
Mr Adamson said police would want to speak to both men today.
The driver was last night reported to be is a serious but stable condition in Hawke's Bay Hospital.