With　the　development　of　urban　architecture,　the　growing　demand　for　larger　public　buildings　is　becoming　challenging　for　indoor　human　evacuation　under　emergencies　such　as　fires.　However,　the　indoor　fire　evacuation　behaviour　of　heterogeneous　crowds　when　including　individuals　with　disabilities　have　not　been　adequately　explained.　Therefore,　this　paper　aims　to　study　indoor　evacuation　characteristics　of　a　crowd　involving　individuals　with　different　types　of　disabilities　(i.　e.,　individuals　on　crutches　and　wheelchair　users)　through　a　modified　social　force　model.　The　computation　and　simulation　is　performed　in　a　room　with　an　exit　in　15　scenarios　involving　varying　number　of　agents　(i.e.,　20,　40　and　60).　The　real-time　trajectories　and　coordinates　of　agents　are　obtained.　It　is　found　that　with　an　increase　in　the　proportion　of　pedestrians　with　disabilities,　individual　evacuation　time　of　agents　increases.　This　tendency　is　consistent　with　results　obtained　from　a　previously　controlled　experiment.　The　average　evacuation　speed　of　agents　is　negatively　impacted　by　the　mixture　proportion　of　individuals　with　disabilities.　The　fundamental　diagrams　acquired　from　the　simulation　are　similar　with　the　experimental　results.　Furthermore,　it　is　discovered　that　the　presence　of　individuals　of　disabilities　in　a　scenario　triggers　higher　crowd　pressure　compared　to　scenarios　involving　all　non-disabled　individuals.　With　an　increase　in　the　proportion　of　pedestrians　with　disabilities,　the　crowd　danger　of　agents　increases,　as　also　consistent　with　the　experimental　findings.　These　findings　are　helpful　for　computer-aided　safe　evacuation　design　to　decrease　heterogeneous　crowd　congestion　during　in-building　fire　evacuation.