The Metropolitan Police says it's looking into whether the substance sprayed into the face of an officer may have been ammonia. He was attacked when he stopped a moped rider in Battersea yesterday afternoon.
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The twins cubs, which were born in June, have been named Bert and Ernie after characters from Sesame Street.
The two victims died from their injuries in hospital after the explosion in Hertfordshire.
Investigations are continuing into the cause of the crash in chigwell which killed both people on board.