Kenya Forest Service (KFS) has admitted that there is an ongoing construction of an eco-hotel in Ngong Forest next to the sanctuary.
It also said the construction process was approved after a public participation exercise.
The admission comes after the Green Belt Movement raised an alarm on Friday of an ongoing construction, terming it an encroachment of the forest.
In a letter addressed to KFS chief executive officer Alexander Lemarkoko, Green Belt Movement also demanded that the identity of the private developer be revealed.