How to find efficient paths for multiple robots in modifiable cluttered environments? This question leads us to the formulation of the new problem of Multi-Robot Navigation Among Movable Obstacles (MR-NAMO). In MR-NAMO, robots must not only plan for the possibility of displacing obstacles as needed to facilitate their navigation, but also solve conflicts that may arise when trying to simultaneously access a location or obstacle. As a first approach to this new problem, we introduce and compare variants of an implicit coordination strategy allowing the use of existing NAMO Algorithms in a Multi-Robot context. We also show how our previously introduced social occupation cost model can improve the efficiency of multi-robot plans with better obstacle placement choices, and how it can be applied in a novel way to find relevant robot placement choices in deadlock situations.