(CNN) -- Relatives of Eunice Kennedy Shriver, a sister of President Kennedy, were summoned Monday to a hospital on Cape Cod, Massachusetts, a source close to the family told CNN.
Eunice Kennedy Shriver speaks at a dinner in honor of the Special Olympics in July 2006.
"It's minute to minute right now," the source said.
Shriver, 88, founder of the Special Olympics, has been in the hospital for several days, her family said, and her relatives were summoned after she suffered a setback, the source said.
Some members of the family flew in to Cape Cod Hospital last week to be with Shriver, including her daughter, Maria Shriver, and Maria's husband, California Gov. Arnold Schwarzenegger, a source said earlier. She was in critical condition then.
Eunice Shriver is the founder and honorary chairwoman of the Special Olympics, which helps 3 million people with intellectual disabilities in 170 countries around the world.
"The Special Olympics movement is saddened to hear that our founder, Eunice Kennedy Shriver, is hospitalized. Our thoughts and prayers are with Mrs. Shriver and her family at this time," organization President Brady Lum said in a statement last week.
"Every day, our Special Olympics family continues to work tirelessly around the world to bring her powerful vision to life to change the lives of people with intellectual disabilities, using sports as the catalyst for respect, acceptance and inclusion."
CNN's Ed Henry contributed to this report.