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.
European praying mantis spotted in Guernsey garden
A rare visitor from Europe is thought to have been attracted by the heatwave summer and southerly winds.
Guernsey's leisure centre reopens after near week-long closure
Authorities say that all traces of Legionella bacteria have been eradicated.
Beau Sejour remaining shut over weekend
Beau Sejour is staying shut this weekend (19 & 20 September), as work continues to eradicate Legionella bacteria detected in the water system.
Flyers advertising polar opposites delivered in Guernsey
A postcard promoting safe drinking and a glossy alcohol flyer end up going through some letter boxes at the same time.
Alex Scott named in England squad
Bournemouth midfielder Guernsey's Alex Scott has been named in Thomas Tuchel's first England squad since the World Cup.
Dangerous cycling on Guernsey roads
E-bikes are being abused by youngsters riding 'three up' on machines designed for an adult and small child.
Closure ongoing at Guernsey's leisure centre
A major effort continues to trace the source of Legionella bacteria and then stop it happening again.
Guernsey's leisure centre closed for another day
The long term solution is the installation of filters to stop Legionella bacteria getting into the water system.
