Despite this latest development, the investigation continues and we still need to hear from anyone who has not yet come forward.
I want to reiterate that we're not looking for anyone else in connection with Christina's murder.
The family, who are still extremely distressed, have been kept up to date with the progress of the investigation. We continue to support them at this very difficult time.
Anyone with information to assist the investigation should call 101 or the independent charity Crimestoppers anonymously on 0800 555 111.
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.
The 16-year-old schoolgirl stabbed to death on a bus in Birmingham during rush hour has been named as Christina Edkins.
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.