After her condition was stabilized, she was transferred to Massachusetts General Hospital in Boston, he said.
Heinz Kerry, 74, was vacationing with Kerry at the family home on Nantucket Island when stricken shortly before 4 p.m., Johnson said. There were no details on the nature or source of her illness. Kerry was with her at the home and remained with her Sunday evening, Johnson said.
Earlier Sunday, Nantucket Cottage Hospital spokesman Noah Brown told reporters Heinz Kerry was in critical but stable condition.
"The family is grateful for the outpouring of support it has received and aware of the interest in her condition, but they ask for privacy at this time," said Johnson.
Heinz Kerry is the widow of former senator John Heinz, R-Pa., and heir to the Heinz ketchup fortune. She and Kerry were married in 1995 on Nantucket.
She said in 2009 that she was bring treated for breast cancer.
Before Sunday, the secretary had planned to come back to Washington on Monday. He and Treasury Secretary Jack Lew were scheduled to host high-level strategic and economic talks with senior Chinese officials on Wednesday and Thursday.
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