The objective of the present work is to assess the risk of spreading of fire between Lithium-ion battery cells initiated by a thermal runaway. In particular it aims at developing means to predict the temperature of cells in the vicinity of an overheated cell during the first 5-7 minutes after the thermal event in a Li-ion cell that has an organic based electrolyte which is flammable. Finite-Element (FE) modelling is used to compute the heat transfer between cells. The spreading model is assessed modeling a scenario where the cells are exposed to a 15 kW propane burner. Two different models where utilized, one that considers the conjugate heat transfer between the surrounding hot gases and the battery cells while the second is a thermal model where the boundary conditions are measured in a mock-up test. The results from the two models are contrasted to experimental data where the heat release rate (HRR) is utilized as an input to the simulation. It is found that the temperature increase in a neighboring cell can be quantitatively estimated in certain cases during the early stages of the fire taking into account the anisotropic thermal conductivity of the cells using the conjugate heat transfer model. Moreover, the thermal model captures the qualitative behavior of the test results, however, the temperature increase is slower in the computational model.