TMZ reports:

The FBI and the LAPD have launched a joint investigation into the suspicious package that was addressed to Bristol Palin at “Dancing with the Stars” this week, TMZ has learned.

Law enforcement sources tell us,both agencies are taking the package’s threat very seriously … and are looking into the possibility that the latest incident is connected to the white powder scare back in 2010.

As we reported, a package containing a white powdery substance was opened on the CBS lot in West Hollywood Wednesday, addressed to Bristol. The package also contained a note, demanding Bristol be removed from the show … or else.

Initial tests in the field revealed the powder was not harmful … just like in 2010, when a suspicious letter was sent to CBS containing a similar threat about Bristol.