A four-day immigration enforcement operation across Northern California netted hundreds of illegal immigrants even after a prominent local official sent out a warning of the impending sweep, U.S. officials said Thursday.

Since Sunday, 232 criminal aliens and other immigration violators were arrested in the San Francisco Bay Area and California’s Central valley, according to Immigration and Customs Enforcement (ICE).

ICE officials said that of the 232 people arrested, 180 of them “were either convicted criminals, had been issued a final order of removal and failed to depart the United States, or had been previously removed” and then re-entered the country illegally.

The Northern California operation drew national attention before it even began when Oakland, Calif., Mayor Libby Schaaf tweeted a statement saying she heard from “multiple sources” of a potential crackdown on illegal immigrants in the area. Schaaf, a Democrat, said she considered it her “duty and moral obligation” to warn illegal immigrants and their families of the operation.

In a statement responding to Schaaf’s Twitter warning, ICE Acting Director Thomas Homan ripped the Oakland mayor, accusing her of putting immigration officers at risk and making it easier for criminals to avoid detection.

“The Oakland mayor’s decision to publicize her suspicions about ICE operations further increased that risk for my officers and alerted criminal aliens — making clear that this reckless decision was based on her political agenda with the very federal laws that ICE is sworn to uphold,” Homan said.

The four-day operation in Northern California was the second in the state since a sweeping sanctuary law took effect at the beginning of the year. Homan and other top administration officials have been highly critical of the law and suggested ICE would carry out more operations in California to compensate for the state’s lack of cooperation on immigration enforcement.

Last month, ICE arrested more than 200 people last month in the Los Angeles area.

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