Republican lawmakers confronted the Democratic mayors of four “sanctuary cities” over immigration policies that they believe have shielded criminal immigrants in the United States illegally, placing Americans and federal officers at risk.

Here's a rundown of several key claims made during the hearing, and our reporting on the issues and numbers referenced by officials.

Denver Mayor Mike Johnston testified on Capitol Hill about the so-called "sanctuary city" policies on Wednesday morning.

Republican congressman James Comer says so-called sanctuary city policies are a nightmare that make American cities more dangerous, as he opens a congressional hearing with Democratic mayors from four

The mayors of four so-called “sanctuary cities” faced tough questions from lawmakers about their policies toward immigrants and how they work with Immigration and Customs Enforcement at a House Oversight and Government Reform Committee on Wednesday.

Johnson and the other mayors defended their immigration policies, saying they have an obligation to protect everyone living in their cities, regardless of their immigration status.