The material is being examined in connection with a complaint of alleged child abuse concerning a 13-year-old boy, Jordan Chandler, the son of a wealthy Beverly Hills dentist.
On Monday, Los Angeles police confirmed that Jackson, 34, the idol of millions of youngsters worldwide, is the subject of a criminal investigation, although detectives declined to elaborate.
The entertainer, who is in Thailand on the first leg of a world tour, has denied any wrongdoing and is said by police to be co-operating fully. Yesterday he cancelled a scheduled concert in Thailand after his doctor said he was suffering from dehydration caused by performance in extreme heat and humidity on Tuesday.
According to court documents filed in Los Angeles, the boy's father - who has been in a custody battle over the child - has sought a court order to prevent his ex-wife from allowing their son to see or communicate with Jackson.
A lawyer for the boy's mother has said that she knew nothing of the allegations until police launched their investigation.
Jackson issued a statement on Tuesday through his lawyer in Los Angeles, Howard Weitzman, saying he believes the investigation will clear his name and that he plans to continue his 'Dangerous' tour.