U.S. Immigration and Customs Enforcement announced on Monday that it will fine three Denver businesses more than $8 million for allegedly hiring more than 100 people without authorization to work in the country.

ICE issued a notice of intent — which was carried out after an investigation found a business knowingly hired and kept employing unauthorized workers — against CCS Denver, Inc., PBC Commercial Cleaning Systems Inc., and Green Management Denver.

It’s not clear whether these are separate business operations or companies under CCS Facility Services, a commercial cleaning and maintenance firm based in Denver.

The CCS Denver and PBC Commercial Cleaning Systems share addresses at 1900 W. Littleton Blvd., the corporate office of CCS Facility Services, according to Secretary of State business filings.

Green Management Denver’s address is listed as 1485 South Lipan St., another location listed on the CCS Facility Services website.

CCS Facility Services and ICE did not immediately respond for comment.

It is illegal for foreign nationals to work without expressed authorization by the U.S. government.

Federal law requires companies that recruit or hire workers to complete what’s called the “Form I-9, Employment Eligibility Verification.”

This process, which the U.S. Citizenship and Immigration Services manages, helps to verify an employee’s identity and authorization to obtain work in America.

Documents that applicants can submit to verify their identity and show they are legally permitted to work include a U.S. passport, a permanent residency card or an employment authorization document.

In 1996, Congress passed the Illegal Immigration Reform and Immigration Responsibility Act, which launched a pilot program that later became E-Verify. The latter is what most companies now use to verify a worker’s eligibility.

E-Verify relies on records from the U.S. Department of Homeland Security and the Social Security Administration to confirm whether a person is eligible to work in the country. The system checks information from the I-9 form against databases maintained by the federal government.

Federal law does not mandate the use of E-Verify. Efforts are afoot in Congress to do so. One proposal would phase in its implementation over time, mandating its use on bigger employers first.

Several states already require companies to use E-Verify.

In Arizona, state law expressly bars companies from hiring foreign nationals without federal work authorization and requires them to run hires through E-Verify. Under Arizona law, a county attorney can bring a civil suit to suspend or revoke a business license for knowingly hiring a worker without federal work authorization.

In 2016, Colorado eliminated its requirements, which mirrored federal law, that employers verify their workers’ status. And in 2021, the legislature repealed requirements that an individual must be lawfully present in the U.S. in order to apply for a professional license or a public works contract.

ICE issued the largest fine to CCS Denver for allegedly hiring 87 immigrants who are not legally allowed to work in the U.S. The company will be fined about $6.2 million, according to a news release from ICE.

The fine was based on a “100% substantive violation rate,” which is calculated by the number of violations, such as illegally hiring workers from outside the U.S. or continuing to employ unauthorized workers.

The number of violations is then divided by the number of I-9 forms the company should have had for an inspection.

The size of the business, good faith of the employer, the seriousness of the violation and the involvement of the workers are also taken into consideration when ICE issues fines.

PBC Commercial Cleaning Systems was fined nearly $1.2 million for “knowingly employing” at least 12 people not authorized to work, ICE said in a news release, based on a 74% violation rate.

Green Management Denver’s fine was about $270,000 for 44 workers and also a 100% violation rate.

“The employment of unauthorized workers undermines the integrity of our immigration system and puts law-abiding employers at a disadvantage,” said ICE Special Agent in Charge Steve Cagen in the announcement. “These penalties reinforce our commitment to uphold the law and promote a culture of compliance.”

CCS Facilities has been operating for more than 40 years and has a presence in 10 states, according to its website. It specializes in janitorial services in large commercial buildings, such as office towers, medical facilities and campuses.