Fiesta 2007 1.6 tdci leak around injectors

[fialeks]

Hi, I am the first time here. I have a problem with my Fiesta 2007 1.6 tdci. There is a leak around injectors, but I am not sure if it is engine oil or diesel leaking from one of the injectors. There is black liquid around the injector seats and the injector 2 is visibly wet. How could I find out if it is the injector of engine oil from under one of the covers? Would diesel look/smell different?