The company has a large and growing outpost in the Bay Area, just south of San Francisco in San Bruno, California.

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Barbara Boxer, who represented the Bay Area 6th District immediately south of Riggs' before winning her Senate seat in 1992.

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South Wales Police said the stretch of river between Leckwith Hill bridge and the mouth of the River Ely near Cardiff Bay Yacht Club will be the area searched on Thursday for Mr Thompson, who is a worker at South Hook LNG gas plant in Pembrokeshire.

BBC: Ben Thompson