'NCIS' Set Hit with Mystery Illness, Cast and Crew Throwing Up During Filming

Folks on the set of 'NCIS' are getting sick ... and sources say the mystery illness has more than a dozen people who work on the show puking.

The long-running CBS program is currently filming in Valencia, CA just outside of L.A. ... and one source tells us at least 18 people on set fell ill Thursday morning.

One show exec told us they have been having Zoom meetings to figure out how to message what happened to everyone involved.

A CBS source tells TMZ it appears to be something like food poisoning, which the source describes as a minor illness with "mild symptoms."

So far, we're told the source of the illness is not known.

We're told they are still in production.