Underground Objects in Hirochi Raceway

I don't know if this is new, but there are some objects under the ground of Hirochi Raceway.

• A cube under one of the garages in the pit lane;
  
  
• Four sheds near the seats at the start/finish line;
  
  
• A piece of curb at the last intersection before the last corner;
  
  
• Four signs near the big round area at the center of the map.
  

 

These are most likely props placed accidentally while making the map, and I'm pretty sure these are known of.