Discrimination - Wrongful Termination - Safety Operator Kett Engineering Employee Review

I was an awarded worker on my assigned project with one of their clients. No issues and one of the top drivers/operators during my tenure. An incident occurred with another contractor where drugs were found n a vehicle. The client and Kett investigated the incident. Random drug tests were issued to those working in that vehicle at the time which included me. I was the only contractor (out of 3) who passed the drug test yet I was still let go after the conclusion of the investigation. One contractor was let go (failed drug test) and another was allowed to return to work (also failed drug test). I had no history of past incidents and I have a clean background. The only relation I had with the contractor that started this whole investigation was ethnicity. I asked HR the reason for my termination and they were reluctant to give one at first. The reason mailed to me with my final check was "we no longer need your services." After days of emailing and calling HR they sent me an email stating I violated their drug policy. If that were the case, the reason for my termination would be a "violation of drug policy" like it was stated to the other contractor who failed their drug test. That still leaves the question of why the other contractor who failed their drug test was able to return while I, who passed my drug test, was let go. This wrongful termination seems to be all rooted in discrimination. So I tell that story to say this, Kett Engineering, Corp. is an agency so you're treated like a classic contract worker. They will say you're a "full-time employee" at Kett Engineering but the contract, benefits (lack of), etc. are structured as a traditional contract worker. Proceed with caution.