Operation “Safe City” snared 27 people from three countries on federal immigration violations in the Bay Area this week.

The U.S. Immigration and Customs Enforcement (ICE) conducted the four-day operation in cities across the country, targeting immigration violations and prioritizing those with criminal convictions, pending charges, gang affiliation, fugitives and those who re-entered the country after being deported, according to an ICE report. Of those arrested in the Bay Area, 23 had previous criminal convictions and four were previously deported.

Nationally, the operation snared 498 people from 42 countries, according to an ICE report that details previous criminal offenses of those detained.

ICE agents arrested a citizen of El Salvador with previous convictions for sex with a minor in San Francisco, and a Mexican citizen with narcotics and felony child cruelty convictions in San Jose. According to the report, these undocumented aliens had previously been released from local jails before ICE could take custody of them.

Tom Homan, ICE acting director, blamed sanctuary jurisdictions for the need to dedicate more resources to these kinds of sweeps.

There is no clear definition of a sanctuary jurisdiction, according to an Atlantic magazine article. The definition is muddied by legal challenges to the Trump administration’s efforts to force local cooperation with enforcement of federal immigration laws. However, sanctuary jurisdictions or cities generally express unwillingness to cooperate with ICE and offer protections to undocumented immigrants.