The Department of Homeland Security’s Immigration and Customs Enforcement (ICE) office announced that it will investigate 1,000 employers nationwide to determine their compliance with employment eligibility verification laws.

The announcement comes just four months after ICE audited 1,000 other employers’ hiring records. The forthcoming investigation reflects the agency’s commitment to increasing annual audits in order to enforce national immigration policies.

Business sectors tied to national infrastructure security—including financial services, health care, food and agriculture, transportation and others—soon will receive notices requesting I-9 documentation, payroll records, copies of immigration filings and Social Security Administration communications, records on independent contractors and other documents.

According to Jackson Lewis, businesses must produce all relevant documents within three business days of receiving a notice from ICE. The firm recommends seeking help from outside counsel in gathering and presenting records.