If someone is assisting the police with their inquiries, it usually means they have been taken to the police station to be asked questions about a crime.

I have cooperated fully with the police and am simply assisting them with their inquiries.

The police are investigating, and a 16-year-old girl is currently assisting police with their inquiries.

I was asked to present myself to the police station to assist police with their inquiries.

We all have a duty to assist the police in their inquiries.

Her boyfriend was taken away to assist police with their inquiries.

See also: assist verb