Well.i have learnt English for years now, but i have just met some problem with the passive voice recently.

i know that in English Grammar,in the Passive Voice,we have some rules about change active sentences into passive sentences,but in this situation,i can't clearly understand that :
A : The Government is building many new schools
=> p : Many new schools is built by the Government (is that correct or not ???)
A : The police arrested several dangerous criminals
=> P : Several dangerous Criminals were arrested by the police (Is that correct or not???)

I know a rule that when the subject is not clearly understand => we can remove this in passive sentence.So, in this situation, "the police and the Government " is not clearly enough.can we remove them in sentences above??? And can you tell me another situation like this???
THanks a lot