Police say the man, who's not yet been named, died at around 6.40pm on 18 September.
Police say the 66-year-old died in a single vehicle accident on the track to Fort Clonque, at Alderney's south-western tip.
They say as investigations are carried out there will be a police presence in the area and ask people to stay away.
The Red Arrows pull out of performing over Guernsey
The RAF display team says aircraft availability and engineering resources mean they cannot leave their Lincolnshire base overnight.
Guernsey's Ladies' Pool reopens after pollution incident
Water quality tests 'excellent' at La Vallette Ladies' Pool.
Passengers at Guernsey Airport told to expect some flight disruption
The advice is check in as usual unless your airline tells you otherwise following national flight chaos.
Guernsey flights impacted by UK air traffic control issue
Some flights between Guernsey and the UK today (8 September) have been cancelled or delayed because of an issue with UK air traffic control.
Engine fault sees private jet diverted to Guernsey Airport
Guernsey Airport operations were disrupted for an hour when a Jersey-bound jet made an emergency landing.
Travel issues ahead of Channel Islands Pride
The lack of an inter-islands ferry is making it difficult for islanders in Jersey to get to Pride 2026 in Guernsey.
WATCH: Car 'sails' from Guernsey to Sark
St John Ambulance and Rescue make the journey to raise funds for the Flying Christine marine ambulance.
Guernsey donates to Nepali disaster relief effort
Overseas Aid gives £50,000 to ShelterBox which has deployed to Nepal.
