Many real component-based systems, so called Control-User systems, are composed of a stable part (control component) and a number of dynamic components of the same type (user components). Models of these systems are parametrised by the number of user components and thus potentially infinite. Model checking techniques can be used to verify only specific instances of the systems. This paper presents an algorithmic technique for verification of safety interaction properties of Control-User systems. The core of our verification method is a computation of a cutoff. If the system is proved to be correct for every number of user components lower than the cutoff then it is correct for any number of users. We present an on-the-fly model checking algorithm which integrates computation of a cutoff with the verification itself. Symmetry reduction can be applied during the verification to tackle the state explosion of the model. Applying the algorithm we verify models of several previously published component-based systems.