Valerie Harper was driven away in an ambulance from the Ogunquit Playhouse in Maine, where she was performing her musical Nice Work If You Can Get It, last night.
According to Entertainment Tonight, the 75-year-old was found unconscious backstage. Responders got to the scene at approximately 9:40 pm and rushed the legendary actress to York Hospital.
The show's director announced: "Valerie wants all of you to know after some fluids and rest she hopes to be right back here on stage later this week."
However, a source close to the situation says it's not looking good for Harper.
After beating lung cancer in 2009, and later being diagnosed with terminal brain cancer in 2013, the Mary Tyler Moore Show star has been fighting for her life for many years, though as of Spring 2015, Harper's cancer had not spread.