Images have now been released of a woman wanted in connection with a racially aggravated assault on a 29-year-old female.
The attack happened on a U4 bus as it went up Judge Heath Lane, Hayes, after leaving Barra Hall Circus on May 13 at 6.30pm. The victim was punched and bitten and also racially abused.
PC Nikki Bryant said: "This was a vicious unprovoked attack on an innocent member of the public. Although this assault took place in May we are still keen to trace the attacker and urge anyone with further information to contact us."
The attacker is described as a white female with long brown straight hair, about 15-16 years old. At the time of the attack she was wearing a grey t-shirt and dark bottoms.
Anyone with information should contact PC Bryant on 020 8721 2757 or Crimestopper anonymously on 0800 555 111.