SAN FRANCISCO (CBS / AP) — The top prosecutors in San Francisco and New York said that the mayor of London is joining their effort to stop the surge of stolen smartphones.

San Francisco District Attorney George Gascon and New York Attorney General Eric Schneiderman will announce on Wednesday that London Mayor Boris Johnson will serve as an international representative for its “Secure Our Smartphones” initiative.

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The lawmakers are urging the leading smartphone manufacturers to create a “kill switch” to render stolen smartphones inoperable.

Johnson has written to similar companies urging them to combat smartphone thefts and plans to meet them in September.

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Gascon and Schneiderman met in June with smartphone representatives in New York City.

Last month, the prosecutors brought in security experts to San Francisco to test Apple’s and Samsung’s newest anti-theft features.

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