Dueling rallies between immigration enforcement supporters and sanctuary city advocates are set to take over Boston City Hall Wednesday as Mayor Michelle Wu testifies on the city’s limited

Boston Mayor Michelle Wu faced forceful questioning by Congressional Republicans in a marathon hearing Wednesday as they pressed her and three other Democratic mayors on their city laws that limit local cooperation with civil immigration enforcement.

The Congressional hearing was part of a federal investigation into so-called "sanctuary cities."Committee Chairman James Comer, a Republican from Kentucky, launched the probe back in January to look into what he described as "the policies of sanctuary jurisdictions and their impact on public safety and federal immigration enforcement.