Special Investigation Agency Indian Investigation Agency is a detective services provider company located in New Delhi. We wish to introduce ourselves as one of the pioneering Private Detective Agency of repute in India having more than 15 years experience in this field. we offer you to the best investigation services. We are catering to the needs of Personal Investigation, Corporate Investigation, Surveillance Detectives, Pre/Post Matrimonial Investigation, Pre/Post Employee Verification, Handwriting Authentication and Personal Advice.