Sen. Tammy Duckworth (D-IL), who recently gave birth, brought her infant daughter as she joined a large demonstration on Capitol Hill on Thursday targeting the Trump administration’s immigration policies.

The protesters were drawing attention to the separation of families seeking asylum at the southern border, a practice that was temporarily halted by an executive order from President Donald Trump.

“I could only imagine what it would be like to have my daughter—my breastfeeding child—ripped away from me the way some of these other moms’ babies have been,” Duckworth said, referring to the Trump administration’s “zero tolerance” policy, which has led to the separation of immigrant families who illegally cross the southern border.

Other Democratic senators also attended the protest, including Sens. Jeff Merkley (D-OR), Kirsten Gillibrand (D-NY), and Ed Markey (D-MA).

Demonstrators were wearing foil to represent the foil-like sleeping bags that children inside the detention facilities were using.

“We have responsibilities under international treaties to treat people with respect when they seek asylum. We have national laws that require it,” Merkley told The Daily Beast.

The Oregon Democrat traveled to southern Texas recently to call attention to the Trump administration policy, which has spurred bipartisan opposition outrage but has yet to lead to a negotiated solution.

Trump’s executive order will likely be subject to legal challenges, and Senate Republicans are still cobbling together a proposal that would permanently end the separation of families while also increasing the number of immigration judges in order to expedite asylum cases. But that measure has yet to attract Democratic support, which is necessary in order to clear the 60-vote threshold. The House failed to pass two conservative immigration bills this week and last week that would have addressed the family-separation issue.

Capitol Police said 575 people were arrested from the Hart building for unlawfully demonstrating. Rep. Pramila Jayapal (D-WA), a progressive who has been outspoken on immigration issues, was among those arrested. The protest took place in the atrium of the Hart Senate office building, where many senators’ personal offices are located.