Charcoal Kiln below Kowloon Pass [????- ]

Walking down the path from Kowloon Pass towards the catchwater, after the path crosses a bridge there's a small, dark depression in the bank on the right of the path. It is close to one of the granite hiking trail markers, visible at bottom left.

A closer look shows the curved shape and burnt earth, with small pieces of charcoal. It looks like the final remains of one of the charcoal kilns.