Law enforcement sources tell TMZ ... Lance's body was discovered at his Studio City home Friday morning around 9:30 AM. His cause of death is currently unclear, but our law enforcement sources say it appears to be natural.

Lance had been doing a press tour for the fourth installment of the 'John Wick' franchise -- he plays Charon in the movie -- and had a guest appearance scheduled for next week on Kelly Clarkson's show.

Lance posted a selfie video on social media Wednesday morning, appearing to be at home with his dogs instead of attending the 'Wick 4' premiere in New York City ... though he never mentioned why he wasn't going to the premiere.

Before his work on 'Wick,' Lance was best known for playing fictional Baltimore Police Department officer Cedrick Daniels on the hit HBO series "The Wire" ... with his character appearing in all five seasons.

Lance also had recurring roles on a bunch of popular TV shows ... including "Fringe," "Bosch," "Oz" and "Lost."

In addition to his success on TV, Lance also acted on the big screen outside the 'Wick' franchise ... with credits in films like "Angel Has Fallen" and "Godzilla Vs. Kong."

Lance has some unreleased projects in the works ... he plays the Greek god Zeus in the upcoming Disney+ series, "Percy Jackson and the Olympians."

Born and raised in Baltimore, Lance earned a music degree from the University of Rochester and he got his MFA from Yale.

Lance was 60.