A large excavator has started digging up an 18-tonne humpback whale buried at a Mid North Coast NSW beach a week ago.

The 12-metre whale died after being beached and its carcass was buried at Port Macquarie's Nobbys Beach because it was too big to be moved.

The 18-tonne whale buried at Nobbys Beach is being exhumed. Credit:AAP/ Port Macquarie-Hastings Council

Port Macquarie-Hastings Council started the exhumation on Monday morning, hoping to have the whale and any contaminated sand removed by the end of the day.

"We are using an excavator with big teeth on its bucket to actually cut the whale in pieces," council's development and environment director Matt Rogers told reporters on Monday.