Around twenty tents have been erected at the Leyton Marsh site where a temporary basketball practice venue is being built.
Work only started on the site this month but construction has already been disrupted by the discovery of a Second World War bomb.
The job is due to be completed by the end of May but lorries have been prevented from making materials deliveries since the protesters arrived over the weekend.
An Olympic delivery Authority spokesman said: ““The basketball training venue is a temporary structure that will be removed within a month of the end of the Games, and the land restored to its previous state.
“The vast majority of Leyton Marsh is completely unaffected. The ODA is committed to building a basketball training facility for the Olympic and Paralympic Games and we regret that action has been taken which has delayed work on the site.”
The Occupy London protesters are supporting local people campaigning as “Save Leyton Marsh”.
One local resident said: “Last Friday a determined bunch of people exercised their rights to use the Marsh freely with a six hour game of boules that resulted in £40,000 of cement being spoiled as the trucks carrying it were blocked from getting on site.
“Lorries containing hard core were prevented from entering the Marsh today and we are hopeful that if we are able to significantly delay building work from taking place we may be successful in halting this destruction of Leyton Marsh.”