( CNN ) -- A number of Chipotle employees across Minnesota were fired after an immigration audit targeted the restaurant chain for allegedly hiring undocumented workers , officials said . `` We are not disclosing a number of people displaced by this , '' company spokesman Chris Arnold said Monday . `` We did lose some restaurant employees in Minnesota following a document review by Immigration and Customs Enforcement . '' The review took place last month and is likely reflective of a shift away from work-site crackdowns against employees -- considered a hallmark practice under the Bush administration -- and toward so-called `` I-9 audits , '' which instead focus on the hiring practices of their employers , according to analysts and a U.S. Immigration official who declined to be named . The I-9 form is an employment eligibility document meant to determine a person 's ability to work legally in the United States . `` At the end of the day , the goal is to ensure that the companies have an authorized , legal workforce and also that employers are aware of their responsibility to ensure the people they hire are lawful , '' the official said . The I-9 strategy is believed to be a more effective use of the agency 's investigative resources , putting the onus on the audited company to take corrective action , the official added . Chipotle has `` done what ICE has asked of us and are looking to put that incident behind us , '' Arnold said . The crackdown coincides with recent judiciary hearings in Arizona in which lawmakers debated proposals to end birthright citizenship for U.S.-born children of illegal immigrants . Nearly one-third of America 's 38 million immigrants are illegal , just under four percent of the total U.S. population , according to recent reports from the Pew Hispanic Research Center and the Brookings Institute , a Washington-based think tank . Of those , many are employed in low-wage restaurants jobs . But analysts debate the broader economic impact of illegal immigration in the United States . Critics often blame the large undocumented workforce for siphoning public resources while forcing a drop in wages or displacing low-skilled U.S.-born workers . Advocates say consumers benefit from lower prices as a result of the lower wages paid to illegal workers , arguing that they fill unskilled labor gaps and create work opportunities for higher-skilled , higher-paid workers who are often native born . Illegal immigration `` nationally , does n't seem to make a significant difference '' to the broader U.S. economy , said Audrey Singer , a senior fellow at the Brookings Institute who studies U.S. immigration policy . `` The real impact is at local levels , '' Singer said , pointing to state and local law enforcement , schools and health care systems that pay for an undocumented workforce that may or may not contribute tax revenue for services rendered . But as record unemployment rates affect cities and towns across the country , immigrants -- particularly illegal immigrants -- are being targeted , she said . CNN 's Christine Romans , Laura Batchelor and Jeanne Meserve contributed to this report .
Chipotle employees in Minnesota were fired after an immigration audit . Restaurant officials say they have complied with ICE requests . Nearly one-third of America 's 38 million immigrants are illegal .