U.S. Immigration and Customs Enforcement said on Wednesday it planned to fine three Colorado companies a total of $8 million following worksite audits, accusing them of employing unauthorized workers.

“The employment of unauthorized workers undermines the integrity of our immigration system and puts law-abiding employers at a disadvantage,” said special agent in charge Steve Cagen in an ICE news release.

“These penalties reinforce our commitment to uphold the law and promote a culture of compliance.”

The agency imposed fines totaling more than $6.1 million on CCS Denver Inc., a company offering janitorial and facility maintenance services, for a 100% violation rate and the employment of at least 87 unauthorized workers.

PBC Commercial Cleaning Systems Inc., which appears to be another cleaning company serving areas from Fort Collins to Denver, was fined nearly $1.6 million for a 74% violation rate and employing at least 12 unauthorized workers.