The FBI is helping the NTSB's staff document the scene, which is standard procedure, it added.
https://www.bbc.com/news/world-us-canada-51272002
Only just come back to the bred fren - was answering bakers call for sauce. Looking at the search results, looks like the 'standard practice' line is being pushed by most MSM players.
NTSB's Investigative Process
https://www.ntsb.gov/investigations/process/Pages/default.aspx
Pic is snippet re: Criminal Activity.