"where is the police" seems a weird sentence in English to me. Is it meant to mean "where is the police station"? Or "where are the police officers? we called them half an hour ago!" In the latter case, "where are the police" sounds more natural to me (British English)
Both are accepted. In american English, you will occasionally hear, "Where is the police?"
I can confirm this. It's considered improper to say 'is' because the police are many but it does happen.
For reference, think of other ways you can describe them.
Have or Has the police arrived? The police have.
Do or Does the police have weapons? The police do have weapons.