LOS ANGELES (AP) — U.S. immigration agents descended on dozens of 7-Eleven stores before dawn Wednesday to open employment audits and interview workers in the largest crackdown on an employer under Donald Trump’s presidency.

Agents tell The Associated Press they targeted about 100 stores from coast to coast in broadening an investigation that began with a 4-year-old case against a franchisee on New York’s Long Island. The hiring audits could lead to criminal charges or large fines.

The action appears to open a new front in Trump’s sharp expansion of immigration enforcement. U.S. Immigration and Customs Enforcement official Derek Benner says Wednesday’s sweep is “the first of many” and “a harbinger of what’s to come” for employers.