Law enforcement sources tell TMZ ... Kabir died Wednesday and authorities are waiting on toxicology results to determine a cause of death.

We're told he had a history of health issues and at this point, investigators believe he may have died from natural causes, though the investigation is still ongoing.

Meanwhile, other sources tell us Kabir was in the San Francisco Bay Area when he died.

Kabir reached the semifinals of "America's Got Talent" in 2021 during season 16 of the NBC talent competition reality show.

He'd been doing stand-up comedy gigs across the country this year ... though it looks like he last performed in early November, at least based on his social media accounts.

Kabir's comedy was also featured on Comedy Central, "Family Guy" and the BBC.

He was 39.