According to TMZ Sports, Zab Judah has launched his own investigation into his June 7 fight with Cletus Seldin - which left Zab hospitalized with a brain bleed.

Judah is demanding to see the drug test results.

Judah -- a two division world champion -- suffered numerous injuries including an intercranial hemorrhage in a TKO loss to Seldin which required emergency surgery after the fight.

Apparently the 41-year-old veteran has hired the law firm of Elefterakis, Elefterakis and Panek to investigate "all circumstances involving the fight."

As part of his investigation, Judah is requesting Seldin's pre-fight urine drug test results so he can see for himself if Seldin was truly clean during the fight.

Judah's attorney wants to be clear that he is making "no formal accusations of misconduct" ... but rather doing their due diligence in the "investigatory stage."

In a statement Judah's attorney says, "To date, our firm contacted the Oneida Gaming Commission as well as the promoter of the fight to obtain the results of the pre-fight urine drug screening. No results have been provided to the Judah camp as of yet."

Seldin has his issues with drug tests in the past

Back in February of 2017, in an out of competition test, Seldin tested positive for high levels of testosterone and he also came up positive for the banned anabolic steroid stanozolol. A few months later he once again tested positive for high levels of testosterone, which caused a planned fight for June of that year to get canceled.