You realise of course that a documentary has to be a film, TV or radio programme which is usually of a certain length. A 10-minute video is not expected to constitute a documentary, for example. In general, we expect a documentary to be half an hour long or more. A more general, and perhaps more useful, translation is "investigations and reports on the police". An example of this kind of usage is "the Sunday Times investigation reports on Fifa".

That's good thank you, the word which I was looking for was documentary.

What form does this reportage take? Is it written in a paper, or a TV program? Is it an official document, or something by a journalist? Is it short, or long? That would give us a better idea to go on

Documentary, autant pour moi !