| Business | Phone |
| Butler & Assoc Investigations 1924 Grant St # 6, Concord 94520 | (925) 969-1505 |
| Investigative Consultants Intl 2290 Diamond Blvd # 203, Concord 94520 | (925) 798-7688 |
| Professional Resource Screen 2400 Bisso Ln # 100, Concord 94520 | (925) 229-3777 |
| Beren Investigative Svc 4480 Treat Blvd # 155, Concord 94521 | (925) 989-8525 |
| Bill Best Investigations Concord 94524 | (925) 676-4925 |
| Brian Olivier Investigations 3143 Clayton Rd, Concord 94519 | (925) 676-7000 |
| Complete Investigations 2045 Mount Diablo St # 105, Concord 94520 | (925) 827-2231 |
| O'Neill Investigative Svc Concord 94520 | (925) 798-3364 |
| Todd Michael & Assoc Po Box 514, Concord 94522 | (925) 680-7107 |