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.
More top news
George Osborne told MPs London would shoulder a large part of his 37% reduction in transport funding.
The prison was originally opened in 1852 as a mixed prison before becoming the first female-only local prison in England in 1902.
The victim was travelling between Seven Sisters and Highbury and Islington when she was assaulted.