The unarmed black teenager whose shooting by a white police officer unleashed riots in a Missouri town was a suspect in a robbery just minutes before he was killed, police say.
The allegation reignited fresh anger in the St Louis suburb of Ferguson, with the 18-year-old's family accusing police of attempting to demean his character.
FBI agents, working with lawyers from the Justice Department and US Attorney's Office, were interviewing witnesses at the time of the shooting, officials said. Incident reports linked Michael Brown to the theft of a US$49 ($57) box of cigars, shortly before he was shot by police on August 9.
Brown's death stirred tensions and renewed a national debate about relations between law enforcement and African Americans.