Translation:¿Quién informó a los periódicos?
I feel as though I'm forgetting something here, but why the need for the "a" in this case?
I wondered this too.
After consulting a dictionary "informar a alguien de algo" is "to inform somebody of something".
But isn't the 'a' in your dictionary definition a 'personal a'? I too don't get the need for it here. Perhaps a native speaker can explain...
It looks like it is. It also gives "El portavoz informó a la prensa", "The spokesman informed the press". Whether or not that makes it the personal a i don't know so hopefully someone else can explain.