Rail replacement buses are running between Pitsea and Grays - with journey times extended by up to an hour.
The disruption is expected to last until lunchtime.
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Police have released CCTV images of a man seen close to the scene of one of the attacks.
A 20-year-old man who died in a triple stabbing outside Parsons Green Tube station has been named by police.
David Jones was responding to London's Fire Commissioner who said the term 'fireman' was outdated and should stop being used.