Safety is a fundamental property for a wide class of systems, which can be assessed through safety analysis. Recent standards, as the ISO26262 for the automotive domain, recommend safety analysis processes to be performed at system, hardware, and software levels. While Failure Modes and Effects Analysis (FMEA) is a well-known technique for safety assessment at system level, its application at software level is still an open problem, especially concerning its integration into certification processes. Fault injection has been envisioned as a viable approach for performing Software-FMEA (SW-FMEA), but it typically requires an advanced development stage where code is available. The approach we propose in this paper, aims to perform software fault injection at model-level, namely on fUML-ALF models obtained from a component-based UML description through transformations proposed in a previous work. Model-level fault injection allows SW-FMEA to assess the effectiveness of safety mechanisms from the early stages of system design. The work in this paper focuses on how the software fault injection is implemented, and on the study of fault propagation through appropriate points of observation to highlight possible violations of requirements, with the identification critical paths.