Officers in Croydon (Metropolitan Police) are investigating incidents this week in which one or more person set light to people sleeping rough.
Detectives believe others may have been targeted and are appealing for any further victims and any witnesses to come forward.
There were two such incidents reported in the area of George Street and Surrey Street in the early hours of Monday, 10 June.
The London Ambulance Service treated two men for minor burns. Sleeping bags or other property was set alight.
At around 05:00hrs on Wednesday, 12 June, a man and a female were stopped by police on George Street in Croydon and arrested.
A 22-year-old man was later charged and is due to appear in court on Thursday, 13 June.
The 17-year-old girl was bailed until a date in July pending further enquiries.
Anyone with information concerning this incident is requested to call police on 101 quoting reference 1018/10 June or Crimestoppers anonymously via 0800 555 111.