U.S. Immigration and Customs Enforcement agents raided four 7-Eleven stores in Portland today during a sting operation, but they made no arrests in the sanctuary city.

The agency arrested 21 people in other parts of the country this morning after dropping in on 98 different 7-Eleven shops before sunrise. The nationwide raid is the latest large-scale enforcement effort to touch Oregon since ICE tried to claim a crackdown on sanctuary jurisdictions more than three months ago.

After September's "Operation Safe City," the agency claimed to make dozens of arrests in sanctuary jurisdictions, including Portland. In reality, ICE agents didn't apprehend anyone in Portland, and only arrested four people in Oregon.

Today's raids specifically targeted one company.

ICE agents had been investigating a systematic reliance on labor performed by undocumented immigrants at the convenience store franchise since 2013.

The federal immigration agents served notices of inspection to four 7-Eleven stores in Portland, alerting the owners to an audit of I-9 employment forms that verify the citizenship or work authorization of employees working in the U.S.

ICE's announcement did not say which four stores in Portland agents visited.

"Today's actions send a strong message to U.S. businesses that hire and employ an illegal workforce: ICE will enforce the law, and if you are found to be breaking the law, you will be held accountable," acting ICE Deputy Director Thomas D. Homan said in a statement.

The investigation of labor and immigration violations at 7-Eleven chains in 2013 was performed by the Homeland Security Investigations branch of ICE, according to a statement issued by ICE spokeswoman Lori Haley.

"In 2013, HSI conducted an investigation into various 7-Eleven franchises that resulted in the arrest of nine franchise owners and managers for conspiring to commit wire fraud, stealing identities and concealing and harboring illegal aliens employed at their stores," the statement said.

Local law enforcement agencies have working relationships with HSI, though local officials insist that the partnership does not contribute to civil immigration-related enforcement efforts. HSI also investigates international crimes like smuggling, human trafficking, and illicit drug rings.

HSI agents can and do arrest undocumented immigrants, according to the federal agency's own statements.

"Under the current administration, all workers encountered during these investigations who are unauthorized to remain in the U.S. are subject to administrative arrest and removal from the country," a spokeswoman said in a statement.