More than 100 restaurants in Washington, D.C., were visited last week by agents from several federal agencies, in a sweep led by U.S. Immigration and Customs Enforcement. They arrived unannounced, some wearing tactical gear, to serve papers that notified the businesses that their employees’ immigration status was being audited.

The targets included high-profile restaurants like José Andrés’s Jaleo, Chang Chang and Chef Geoff’s, whose owner, Geoff Tracy, is married to the CBS News correspondent Norah O’Donnell.

The action was part of a broader sweep in the district that led to nearly 200 arrests, according to ICE. In a statement, the agency said it had “targeted the most dangerous illegal offenders” in the capital. “These arrests make clear that violating our nation’s immigration laws will not be ignored.”

None of the arrests resulted from the agents’ visits to restaurants, an ICE spokesman said. Still, the broad scope and unusual nature of the action (such audits are usually conducted by mail or email) has sent fear throughout the restaurant business, which relies heavily on the labor of undocumented workers

Lawyers from the National Immigrant Law Center, private firms and local and national restaurant associations have been producing “Know Your Rights” documents, and contacting clients with guidelines on how to respond. All said that they expect these actions to increase nationally as the Homeland Security Department, which includes ICE, increases enforcement. (ICE declined to say whether similar actions were planned around the country, citing the safety of its employees.)

The lawyers offered these basics about federal laws and guidelines. ICE did not respond to requests for comment on that information.