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.
Guernsey bags third in the Island Games 2025
Guernsey finishes in a hard-fought third place, behind Jersey in second, and the Faroe Islands in first.
Guernsey artists showcased at harbour terminal
Guernsey Ports is collaborating with island artists to brighten up the harbour terminal.
Guernsey in third going into final day of Orkney Island Games
Guernsey's women swimmers excel on the penultimate day of competition at the Orkney Island Games.
Free bikes provided for children in Guernsey parks this summer
BeActive is providing balance bikes for public use in the island's parks this summer.
Five more years of boating lessons for Bailiwick schools
School children across the Bailiwick will continue to get free boating lessons for the next five years.
La Societe to protect two Guernsey streams
A Guernsey preservation group wants listed status for the Water Lanes and the stream near the Vale Church.
Guernsey women road cyclists win gold
There have been more golds in Orkney for the cyclists and the successful women swimmers.
States buy one of Guernsey's largest brownfield sites for housing
The States and the Channel Islands Co-op have agreed a deal to progress the long-awaited development of Leale's Yard.
