David Friend. Watching the World Change. (5).

Friend, David. Watching the World Change: The Stories Behind 9/11. I.B. Tauris. 2006. London / New York.

On photographing the remains - after noting who had removed them, and where they had been removed from - Friend writes, quoting from an unidentified NYPD detective and forensic photographer:

The remains would then be rendered in color Polaroid. "Not film, not digital. You couldn't take a chance that the film wouldn't come out or that the digital file would be compromised." (p68)