SAN FRANCISCO (AP) — The U.S. Immigration and Customs Enforcement spokesman in San Francisco has resigned after becoming frustrated by Trump administration statements about a recent sweep targeting illegal immigration.

James Schwab told the San Francisco Chronicle on Monday that top officials repeatedly said roughly 800 immigrants escaped arrest because of Oakland Mayor Libby Schaaf's Feb. 24 warning about the four-day operation.

U.S. Attorney General Jeff Sessions said he had learned the agency failed to make 800 arrests because of the mayor's warning.

The federal agency's acting director, Thomas Homan, said Schaaf's warning caused about 800 "criminals" to elude capture.

Schwab says the statements were misleading because the agency never captures everyone on its target lists.

ICE spokesperson Liz Johnson said in a statement that the mayor's warning "clearly had an impact" but the agency can't put a number on how many people avoided arrest.

Trump tweeted Tuesday that "thousands of dangerous & violent criminal aliens are released as a result of sanctuary policies" and are "set free to prey on innocent Americans."

The president tweeted from aboard Air Force One as it flew him to California for his first visit to the state as president. Trump is scheduled to visit eight prototypes for the massive wall he wants built along the U.S. border with Mexico. Protests for and against the wall are planned.

The trip comes as the Trump administration battles California over its refusal to cooperate with federal immigration authorities.

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Information from: San Francisco Chronicle, http://www.sfgate.com