| Business | Phone |
| Daniels Circle D Investigation Grass Valley 95945 | (530) 272-6036 |
| Aries Investigative Svc 123 Rockwood Dr, Grass Valley 95945 | (530) 274-7890 |
| Askari Investigative & Legal Grass Valley 95949 | (530) 268-0751 |
| Backtrack Investigations 11900 Sutton Way, Grass Valley 95945 | (530) 268-3800 |
| Carlson Investigations 149 Woodcrest Way, Grass Valley 95945 | (530) 274-2803 |
| Pioneer Investigations 20674 Hannan Bar Jh Pl, Grass Valley 95949 | (530) 268-3637 |
| Technology Investigative Svc 12012 Sutton Way, Grass Valley 95945 | (530) 274-1976 |