This video posted on the official NASCAR YouTube channel shows the moment that at least 10 cars were involved in a crash at the Daytona Speedway just before the end of the Nationwide race.
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The star said that "uncertainty" in the world had led him to take up a second European passport.
He said NFL stars who refuse to stand for the national anthem in silent protest over human rights should be fired.
The children - who are two of three triplets - were found not breathing at a property in Bridgend, Wales.