Call dedicated hotline 0800 096 0095 if you were on the no. 9 bus at the time of the incident or if you have info on the suspect's movements
At the moment there is no known link between Christina and the 22y/o man in custody. Murder weapon has not yet been traced.
Detectives exploring lots of possible motives but at the moment this appears to be a totally random attack.
A 22-year-old man was arrested in connection with the fatal stabbing of a "bright and popular" teenager on a bus as she travelled to school.
West Midlands Police have launched a manhunt after a 16-year-old girl was fatally stabbed on a bus in Birmingham on her way to school.