diff --git a/pysd/py_backend/external.py b/pysd/py_backend/external.py
index 35e4ffae..df18110a 100644
--- a/pysd/py_backend/external.py
+++ b/pysd/py_backend/external.py
@@ -29,11 +29,23 @@ def read(cls, file_name, sheet_name):
         if file_name.joinpath(sheet_name) in cls._Excels:
             return cls._Excels[file_name.joinpath(sheet_name)]
         else:
+            # get the function to read the data based on its extension
+            read_kwargs = {}
+            ext = file_name.suffix.lower()
+            if ext in ['.xls', '.xlsx', '.xlsm', 'xlsb', 'odf', 'ods', 'odt']:
+                read_func = pd.read_excel
+                read_kwargs['sheet_name'] = sheet_name
+            elif ext == '.csv':
+                read_func = pd.read_csv
+            else:
+                read_func = pd.read_table
+            # read the data
             excel = np.array([
                 pd.to_numeric(ex, errors='coerce')
                 for ex in
-                pd.read_excel(file_name, sheet_name, header=None).values
+                read_func(file_name, header=None, **read_kwargs).values
                 ])
+            # save data for future retrievals
             cls._Excels[file_name.joinpath(sheet_name)] = excel
             return excel
 
@@ -109,34 +121,27 @@ def _get_data_from_file(self, rows, cols):
             depending on the shape of the requested data
 
         """
-        ext = self.file.suffix.lower()
-        if ext in ['.xls', '.xlsx', '.xlsm']:
-            # read data
-            data = Excels.read(
-                self.file,
-                self.sheet)[rows[0]:rows[1], cols[0]:cols[1]].copy()
+        # read data
+        data = Excels.read(
+            self.file,
+            self.sheet)[rows[0]:rows[1], cols[0]:cols[1]].copy()
 
-            shape = data.shape
+        shape = data.shape
 
-            # empty cells
-            if shape[0] == 0 or shape[1] == 0:
-                raise ValueError(
-                    self.py_name + "\n"
-                    "The cells are empty.\n"
-                    + self._file_sheet
-                )
-
-            # if it is a single row remove its dimension
-            if shape[1] == 1:
-                data = data[:, 0]
-            if shape[0] == 1:
-                data = data[0]
-            return data
+        # empty cells
+        if shape[0] == 0 or shape[1] == 0:
+            raise ValueError(
+                self.py_name + "\n"
+                "The cells are empty.\n"
+                + self._file_sheet
+            )
 
-        raise NotImplementedError(
-            self.py_name + "\n"
-            f"The files with extension {ext} are not implemented"
-        )
+        # if it is a single row remove its dimension
+        if shape[1] == 1:
+            data = data[:, 0]
+        if shape[0] == 1:
+            data = data[0]
+        return data
 
     def _get_data_from_file_opyxl(self, cellname):
         """
@@ -1054,8 +1059,19 @@ def get_subscripts_cell(self, row_first, col_first, lastcell):
         if col_last is not None:
             read_kwargs['usecols'] = np.arange(col_first, col_last+1)
 
-        data = pd.read_excel(
-            self.file, self.sheet,
+        # get the function to read the data based on its extension
+        ext = self.file.suffix.lower()
+        if ext in ['.xls', '.xlsx', '.xlsm', 'xlsb', 'odf', 'ods', 'odt']:
+            read_func = pd.read_excel
+            read_kwargs['sheet_name'] = self.sheet
+        elif ext == '.csv':
+            read_func = pd.read_csv
+        else:
+            read_func = pd.read_table
+
+        # read the data
+        data = read_func(
+            self.file,
             skiprows=row_first-1,
             dtype=object,
             **read_kwargs
diff --git a/tests/data/not_implemented_file.ods b/tests/data/not_implemented_file.ods
deleted file mode 100644
index a56eb466..00000000
Binary files a/tests/data/not_implemented_file.ods and /dev/null differ
diff --git a/tests/pytest_types/external/pytest_external.py b/tests/pytest_types/external/pytest_external.py
index e5296531..4f3aeaff 100644
--- a/tests/pytest_types/external/pytest_external.py
+++ b/tests/pytest_types/external/pytest_external.py
@@ -1968,34 +1968,6 @@ class TestWarningsErrors():
     Test for the warnings and errors of External and its subclasses
     """
 
-    def test_not_implemented_file(self, _root):
-        """
-        Test for not implemented file
-        """
-        import pysd
-
-        file_name = "data/not_implemented_file.ods"
-        sheet = "Horizontal"
-        time_row_or_col = "4"
-        cell = "C5"
-        coords = {}
-        interp = None
-        py_name = "test_not_implemented_file"
-
-        data = pysd.external.ExtData(file_name=file_name,
-                                     sheet=sheet,
-                                     time_row_or_col=time_row_or_col,
-                                     root=_root,
-                                     cell=cell,
-                                     coords=coords,
-                                     interp=interp,
-                                     final_coords=coords,
-                                     py_name=py_name)
-
-        error_message = r"The files with extension .ods are not implemented"
-        with pytest.raises(NotImplementedError, match=error_message):
-            data.initialize()
-
     def test_non_existent_file(self, _root):
         """
         Test for non-existent file