NCIS Hit with Mystery Illness as At Least 18 Cast and Crew Members Throw Up on Set: Report

Sonja Flemming/CBS NCIS

The production of NCIS has reportedly been hit with a mystery health issue.

At least 18 cast and crew members from the hit CBS procedural, which is being filmed in Valencia, California, came down with a sudden illness Thursday morning that included vomiting, according to TMZ.

A source told the outlet that "mild symptoms" seem to point to potential food poisoning, but there has been no confirmation of a cause.

An executive for NCIS had no comment when reached by PEOPLE.

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Sonja Flemming/CBS NCIS

NCIS is currently on its 19th season and recently said goodbye to its lead character, Special Agent Leroy Jethro Gibbs, played by Mark Harmon.

Harmon, 70, played Gibbs for 18 seasons. During episode four of season 19, the beloved character — who was nearly killed during the season 18 finale — left his job for good, opting to stay in Alaska indefinitely after solving a case.

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"I'm not going back, Tim," Gibbs told Special Agent Timothy McGee (Sean Murray) while fishing. "I'm not going back home."

Gibbs then told McGee that he "could not have hoped for anyone better" to work with over the past 18 years before the partners hugged, closing out the emotional scene.

RELATED VIDEO: Mark Harmon Departs NCIS After 18 Seasons: He's "Always Going to Be a Part of the Show"

Speaking to PEOPLE in 2019, Harmon revealed what would ultimately cause him to leave the series after nearly two decades.

"If there's ever a time where the writers are walking into the room and going 'I don't know what to do,' then I think we all have to look at each other and call it a day," he said at the time. "But we're not there yet."

Harmon also expressed his gratitude for his long-running spot on the show. "I've been around long enough to know what this is. That commitment is part of what I signed up for; I know when this show ends that's it — there won't be anything else like this for me," he shared.

The action drama's current cast includes Murray, 44, plus Brian Dietzen, Diona Reasonover, Wilmer Valderrama, Rocky Carroll, Gary Cole and David McCallum.