Linking to external dynamic library with mex on Mac OSX 10.8.4

Hello, I am trying to link to an external dynamic library in R2012b running on Mac OSX 10.8.4. Running the following command

mex -I<path to header> -L<path to library> -v <filename> -l<libname>

yields an Undefined symbols for architecture x86_64: error. The DYLD_LIBRARY_PATH variable was set to include the library path. A simple test console applications utilizing library functions when built and linked to the library using gcc.

Does anyone have any ideas or advice, I have searched extensively for more information but have found no solution.

Thanks David

Is your MATLAB 64-bit, but the library 32-bit?