A teenager has been arrested on suspicion of starting a bus fire.
The blaze, which caused £50,000 worth of damage, was started on the top deck of a 154 bus as it travelled through Sutton.
The fire raged at the back of the double-decker as four passengers were coming up the stairs on Saturday May 3.
Ten other commuters were downstairs at the time, including a disabled person on crutches.
A 16-year-old male was taken in by police on Thursday May 29.
The fire was started as the bus travelled from the Roundshaw Estate to Wallington Town Centre.
Police were called at 08:30am as fire fighters from London Fire Brigade tackled the blaze.
The teenager, who cannot be named, was arrested at his home address and has been bailed pending further enquiries.
The bus has been taken out of service.