Amid tensions over President Trump’s immigration crackdown in Minnesota and beyond, federal agents were told this week that they have broader power to arrest people without a warrant, according to an internal Immigration and Customs Enforcement memo reviewed by The New York Times.

The change expands the ability of lower-level ICE agents to carry out sweeps rounding up people they encounter and suspect are undocumented immigrants, rather than targeted enforcement operations in which they set out, warrant in hand, to arrest a specific person.

The shift comes as the administration has deployed thousands of masked immigration agents into cities nationwide. A week before the memo, it came to light that Todd M. Lyons, the acting director of the agency, had issued guidance in May saying agents could enter homes with only an administrative warrant, not a judicial one. And the day before the memo, Mr. Trump said he would “de-escalate a little bit” in Minneapolis, after agents fatally shot two people in the crackdown there.

The memo, addressed to all ICE personnel and signed on Wednesday by Mr. Lyons, centers on a federal law that empowers agents to make warrantless arrests of people they believe are undocumented immigrants, if they are “likely to escape” before an arrest warrant can be obtained.

ICE has long interpreted that standard to mean situations in which agents believe someone is a “flight risk,” and unlikely to comply with future immigration obligations like appearing for hearings, according to the memo. But Mr. Lyons criticized that construction as “unreasoned” and “incorrect,” changing the agency’s interpretation of it to instead mean situations in which agents believe someone is unlikely to remain at the scene.