12:07 PM PT -- Sources connected to Luke tell TMZ doctors have placed him in a medically induced coma. The stroke, we're told, was "massive." When paramedics arrived at his home he was responsive and talking but his condition deteriorated and he was rushed to the hospital.
8:38 AM PT -- A rep for Luke tells TMZ ... he is currently under observation at the hospital.
Paramedics responded to Luke's home in Sherman Oaks around 9:40 AM. We know the call came into the fire department for someone suffering a stroke, and Luke was transported to a nearby hospital. It's unclear what his condition is right now.
The 52-year-old who stars as Archie's dad, Fred Andrews, on "Riverdale" ... had been shooting episodes recently in L.A. on the Warner Bros. lot.
Luke's medical crisis coincidentally struck on the very same day Fox announced it will reboot "Beverly Hills, 90210" -- the show on which he shot to fame, playing Dylan McKay in the 90s.
While his former costars -- Jennie Garth, Ian Ziering, Jason Priestly, Brian Austin Green, Tori Spelling and Gabrielle Carteris -- will be on the revived series, Luke has not signed on to the project.
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