(CNN) -- Civil rights activist Dorothy Height, 98, remained in "very serious, but stable condition" Saturday, her friend and spokeswoman said.
A flurry of rumors about Height's death appeared Saturday on the Internet, particularly on the social networking site Twitter, where her name was a trending topic. Wikipedia also briefly reported Height's death.
Height remains hospitalized, according to Alexis Herman, her friend and former secretary of labor under President Bill Clinton. Height was admitted to Howard University Hospital earlier this week. Further details about her condition were not immediately available.
"We are grateful for the professional care of her doctors," Herman said in a written statement. "We especially thank everyone for your thoughts, prayers and support during this challenging time."
Height, who turned 98 Wednesday, is chair and president emerita of the National Council of Negro Women. In the 1960s, she worked alongside civil rights pioneers, including the Rev. Martin Luther King Jr., future U.S. Rep. John Lewis and A. Philip Randolph.
She has been active in civil rights since the New Deal era, according to her biography on the National Council of Negro Women's Web site.
As a leader of the United Christian Youth Movement of North America beginning in 1933, "she worked to prevent lynching, desegregate the armed forces, reform the criminal justice system and for free access to public accommodations," the site says.
She was elected president of the NCNW in 1957 and held the post until 1998.
CNN's Lindy Royce contributed to this report.