The horn sounded to clear spectators from the course with major winners Francesco Molinari, Jason Day and Brooks Koepka all sharing the clubhouse lead at seven-under.
Players were greeted by steady rain as play began on Friday but the skies cleared allowing over half of the 87-player field to complete their rounds before action was halted.
Several prominent players were still on the course when the horn blasted, including Rory McIlroy and Tiger Woods, who had just hit his tee shot on the par-three 12th.
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(Reporting by Steve Keating. Editing by Toby Davis)
