RWObj_CafReader crash when attempting reading .mtl file from an obj

Handle(XCAFApp_Application) anApp = XCAFApp_Application::GetApplication();

Handle(TDocStd_Document) anXCAFDoc;
anApp->NewDocument("MDTV-XCAF", anXCAFDoc);

RWObj_CafReader aReader;

aReader.SetDocument(anXCAFDoc);

Message_ProgressRange pr;
aReader.Perform(filename.c_str(), pr);

i have this part of code that visualizes an obj into the opencascade scene. I can visualize the OBJ, but i can't see the materials that are referenced in the first line of the obj file.
for instance, if the obj has smt like:
mtllib 3D.mtl
and the very simple mtl file has something like:
newmtl 0_0
Kd 1.0 0.5 0.0

the RWObj_CafReader Perform method gives me an exception, so i cant manage to visualize obj with materials.

Best regards