Premise: London Metropolitan Police commissioner Sir Ian Blair has confirmed that there have been three small explosions on tube trains at Warren Street, Oval and Shepherd's Bush stations, and another small explosion on a No. 26 bus on Hackney Road in Bethnal Green. The London Ambulance Service has not found any injured people, but one person has reported themselves to a local hospital. It is not yet known if this is connected with the blasts.
Hypothesis: On Hackney Road, it was a No. 17 bus that had a small explosion.