Updated at 5:41 PM:
Teresa Heinz Kerry, the wife of Secretary of State John Kerry and one of the nation’s leading philanthropists, was in fair condition Monday at a Boston hospital after "exhibiting symptoms of a seizure" a day earlier, according to a source close to the family.
Earlier Monday, a separate medical source who treated her told NBC News the ailment was "a grand mal seizure of unknown origin". The source described it as "an electrical storm in the brain."
Heinz Kerry had been rushed by ambulance to a Nantucket hospital from her family's home on the Massachusetts island just after 3:30 on Sunday. She and Kerry had been vacationing there over the holiday weekend.
Kerry accompanied his wife to Nantucket Cottage Hospital, where she was admitted in critical condition but was stabilized by doctors there, according to a hospital spokesperson. She was then transferred to Massachusetts General Hospital late Sunday, his spokesman Glen Johnson said.
"After conducting tests overnight and this morning, doctors at Massachusetts General Hospital have upgraded Mrs. Teresa Heinz Kerry's condition from critical to fair," Johnson said in a statement Monday, noting that she is undergoing further evaluation. No further details about her health have been released.
Heinz Kerry, 74, is a breast cancer survivor and an outspoken advocate of preemptive screening and early detection. She underwent treatment at Massachusetts General Hospital in late 2009 as well as at a Washington, D.C. area hospital.
She is the widow of the late Senator John Heinz, who died in a plane crash over a Pennsylvania schoolyard in 1991. Seven people, including two children, died in the accident.
As head of the Heinz Family Foundation and heir to the ketchup fortune of the same name, Heinz Kerry manages numerous endowments, focused largely on environmental activism and social programs.
She and Kerry, then a Senator from Massachusetts, married in 1995. She is the mother of three adult sons from her first marriage.
Kerry returned to the United States just before the start of the July 4 holiday weekend after a nearly two-week trip to the Middle East and Southeast Asia. During that time, he met with Israeli Prime Minister Benjamin Netanyahu and President Mahmoud Abbas of the Palestinian Authority in an effort to re-start the peace process. He indicated a desire to return to the region at the end of the week, and was due back in Washington later Monday to prepare for meetings with Chinese leaders. It is unclear how his wife’s health will impact his travel plans later in the week.