Inspectors from the Health and Safety Executive (HSE) are at the scene of an incident at the Royal estate at Sandringham.
A spokesman for the HSE said:
No formal investigation has been launched, but we do have inspectors at the scene with police who are making initial enquiries.
More top news
Showers dying out during this evening to leave a dry night with some long clear spells leading to a frost by morning. Lows -1 deg C
A protest march has been held in Huntingdon over plans to merge two local hospitals to save money.
A protest march has taken place in Huntingdon over plans which could see Hinchingbrooke Hospital merge with Peterborough City Hospital