Police is or police are

Answer 1

Use the third person, plural form 'are' when referring to police in general. The word police is an aggregate noun, a word representing an indefinite number of parts; aggregate nouns have no singular form.

When referring to a single person or a specific department, use the third person, singular 'is'. Examples:

The police are blocking off the street where the accident occurred.

A police officer is getting information from the neighbors.

The police department is at the corner of First and Main streets.

Answer 2

The word police is a group noun that uses a plural verb, like people. It is already plural.

"Police are canvassing the area."

"The police are investigating."

To express the singular of police, you would have to use another noun, such as policeman, policewoman, or police officer.

e.g. I reported it to the police. A policeman came and filed a report.