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.
WATCH: Last Blue Islands plane leaves Jersey
The last plane that formed part of Blue Islands’ fleet has left Jersey Airport.
New woodland for Alderney's 80th Homecoming
Alderney will get a Royal Visit on 15 December and over the weekend a new area of woodland will be planted out.
Guernsey States 'in talks' with easyJet
Guernsey's Economic Development Committee has confirmed that it is in talks with 'a number of airlines' about island routes.
Guernsey's airline Aurigny takes on six new First Officers
Recruits are the first to come from a partnership between a flying academy, Norse Atlantic and Aurigny.
Call for more transparency over Guernsey Electricity's charges
Thousands complete a survey that calls for price and cost transparency at Guernsey Electricity.
Guernsey Police investigate 'unexplained death' in St Peter Port
Specialist officers are examining a property in Mill Street following an 'unexplained death'.
Senior Guernsey politician to stay on committee during police investigation
It has been confirmed that Deputy Gavin St Pier will continue as P&R committee Vice President and Treasury lead while a police investigation continues.
Iconic Guernsey restaurant to close before Christmas
Da Nello in the Pollet has been in business for 47 years but the owners are now retiring.
