"The lead guide abseiled down to where he had fallen to [approximately 100m below the road] and determined that he showed no signs of life."
The Ministry of Foreign Affairs and Trade confirmed it was aware of the death of a New Zealander in Bolivia and was providing consular support.
No more information could be confirmed due to privacy considerations.
Bolivia is in central South America. The country covers sections of the Andes Mountains and Amazon Basin rainforest.
Matthew's said the company was conducting its own investigation and co-operating with local and international authorities to uncover as many details as possible about the accident.
Gravity Assisted Mountain Biking was established by Matthews in 1998.
"Gravity has safely guided more than 100,000 clients down the road during this time, while Gravity has previously had one customer die of a heart attack, this is the first rider we have had die in a bicycle accident."