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.
'World-class' Guernsey golf course to open this summer
La Grande Mare Golf Course has been extended and reconfigured over seven years.
Guernsey helps the medical response to Ebola in central Africa
Overseas Aid has given £50,000 to a UK charity for protective clothing as they work among Ebola victims in the DRC.
Guernsey to consider social media ban for under-16s
Guernsey politicians are responding after the UK announced a social media ban for under 16s.
Guernsey footballer shares pics from England squad visit
Guernsey's Alex Scott has given fans a glimpse behind the scenes training with the England squad, by sharing a selection of photos on Instagram.
Guernsey endurance athlete on schedule for record breaking walk
Mark Prevel says he has 'banked some miles' to make the remaining two weeks easier.
First stage of Guernsey's Castle Bridge reconstruction begins
There will be full pedestrian access to the Castle and Lighthouse during the eight week project.
Guernsey cyclist becomes MBE in King's Birthday Honours
Ian Brown, known for his cycling achievements and extensive charity work, has been made an MBE.
Guernsey students heading to university to receive Meningitis B vaccine
A UK Government programme to offer the meningitis B vaccine to Year 13 pupils, and those under 25 starting university this autumn, is set to be extended to Guernsey.
