Vice President Kamala Harris warned of mass deportations and “massive detention camps” if former President Donald J. Trump returned to office, telling an audience of Hispanic leaders in Washington that his immigration agenda was a danger to the country.

“We all remember what they did to tear families apart,” Ms. Harris said at a Congressional Hispanic Caucus event, part of an effort to build up support among Latino voters. “And now they have pledged to carry out the largest deportation, a mass deportation, in American history.”

The crowd turned from jovial to silent as the vice president asked them to dig deeper into Mr. Trump’s proposals, which include plans to round up undocumented people on a mass scale and to detain them in camps pending their deportation.

“Imagine what that would look like and what that would be,” Ms. Harris said. “How’s that going to happen? Massive raids? Massive detention camps? What are they talking about?”

Ms. Harris paired the attack on Mr. Trump’s agenda with pledges to prioritize security at the border and provide an “earned pathway to citizenship.” She has sought a balancing act as polls have shown some Latino voters trust Mr. Trump over Democrats on the border.

Many Latino voters have also warmed to Mr. Trump’s immigration proposals, including his plan for mass deportations, which U.S. officials say would encounter major legal and logistical hurdles. But Mr. Trump remains unpopular with Latino voters overall, and many Latino voters want to see both tough border security measures and a pathway to citizenship for undocumented immigrants.