Scotland Yard said two passengers still remain trapped on the bus and two uniformed police officers who were travelling on the bus, are among the 30 injured.
London Ambulance Service say 6 people are seriously injured.
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Calum McSwiggan posted a photo on Instagram as he lay in a hospital bed after the alleged attack.
The London mayor publicly backed defeated candidate Owen Smith in the contest which saw Mr Corbyn re-elected party leader.
Police described it as a "growing sink hole" and it's unclear when the road will reopen.