SAN FRANCISCO (AP) — A federal immigration official says about 800 people living illegally in Northern California avoided being arrested because Oakland Mayor Libby Schaaf warned that immigration raids were upcoming.

U.S. Immigration and Customs Enforcement chief Thomas Homan told “Fox and Friends” Wednesday that Schaaf’s action was “no better than a gang lookout yelling `police’ when a police cruiser comes in the neighborhood.”

READ MORE: 'It's Indefensible': VA Spent Millions In Taxpayer Dollars To Perform Experiments On Cats

Homan says the Justice Department is looking into whether Schaaf obstructed justice.

READ MORE: 1 Dead After Short Pursuit Ends In Fiery Crash Near The Grove; Suspect In Custody

The mayor warned residents Saturday night of large-scale raids by immigration agents in the San Francisco Bay Area.

The agency on Tuesday said that agents arrested more than 150 people in California after the mayor’s warning in a sweep that covered cities from Sacramento to Stockton in California’s Central Valley agricultural heartland.

MORE NEWS: Union Rescue Mission CEO Andy Bales Won't Stop Until Homelessness Is No Longer An Issue

(© Copyright 2017 The Associated Press. All Rights Reserved. This material may not be published, broadcast rewritten or redistributed.)