Giant clothing retailer, Abercrombie & Fitch was fined $1 million by the U.S. Immigration and Customs Enforcement in Detroit on Tuesday for failure to verify the employment eligibility of its workers who were based at its Michigan stores.

The $1 million fine was one of the largest fines ever imposed on an employer by the U.S. Immigration and Customs Enforcement (ICE) in Michigan to date.

According to ICE’s spokesperson Khalid Walls, Abercrombie & Fitch was not able to produce sufficient documents to prove the employment eligibility of its workers.

Since November 6, 1986 the law requires that all employers should request employees to fill up forms I-9 at the time of hire; employers should also keep a copy of the forms in their employees’ files. The Form I-9 compliance is meant for verification of workers’ employment eligibility to ensure they are legally allowed to work in the United States. An I-9 compliance also means that employers must verify employees’ documentation such as their birth certificates in the U.S. to ensure they are eligible to work or valid immigration documents showing employment authorization such as employment authorization card, an H-1 or working visa.

“The heavy fine serves as a reminder to all employers, that the federal government is serious about ensuring employers play their roles in checking and reviewing the employment eligibility of their workers. Employees’ documents are equally significant to the federal government as their financial documents are,” said Walls.

Headquartered in New Albany, Ohio, Abercrombie & Fitch is a global brand retailer specializing in casual wear and accessories and currently operates 10 Abercrombie & Fitch stores and 16 Hollister stores in Michigan.

Abercrombie & Fitch did not respond to a call for comment on the fine on Tuesday.

According to Walls, ICE started to investigate Abercrombie’s case after receiving an anonymous tip that there were “severe deficiencies with their documents.”

During an audit, ICE discovered that Abercrombie had numerous technical problems in the retailer’s electronic I-9 verification system resulting in the failure to produce their employees’ documentation upon request.

By filling up a form I-9, a potential employee must provide one or more documents listed in the I-9 to the employer in order to establish identity and authorization to work. Employers are required under the federal immigration law to perform verification of potential employees’ identity and work authorization documents before hiring takes places. Failure to verify employees’ documents and keep their forms I-9 as proof that verification process has taken place constitute a violation of the U.S. business immigration law.

A statement released by the government stated that Abercrombie & Fitch provided full cooperation to ICE officials throughout the investigation, and did not intentionally hire workers who do not possess employment authorization or who have entered the country illegally.