Then-Sen. John Kerry (L) and his wife, Teresa Heinz Kerry, awaiting the start of the hearing nominating Senator Kerry to become the next secretary of state on Jan. 24 in Washington. (JIM LO SCALZO/EPA)

The condition of Teresa Heinz Kerry, the wife of Secretary of State John F. Kerry, was upgraded from critical to fair Monday morning, the secretary’s spokesman said.

The spokesman, Glen Johnson, said that Heinz Kerry, 74, was “undergoing further evaluation” at Massachusetts General Hospital in Boston, where she was admitted Sunday after being airlifted from a smaller hospital near the family home on Nantucket Island.

Kerry, Heinz Kerry’s son and other family members were with her, Johnson said.

Kerry’s office has issued no details on Heinz Kerry’s illness. A source close to the family said that she was taken to the Nantucket emergency room Sunday afternoon after exhibiting “signs of a seizure” but that no diagnosis has been made.

Heinz Kerry, an heir to the Heinz ketchup fortune, was the widow of Sen. John Heinz (R-Pa.), who died in 1991. She and Kerry were married in 1995 on Nantucket.

Before his wife became ill, Kerry was due in Washington on Monday for meetings on the Egypt crisis and for high-level strategic and economic talks with senior Chinese officials later in the week.

Kerry returned Wednesday from a two-week, around-the-world trip that included intensive negotiations with Israeli and Palestinian leaders on possible new Middle East peace talks. He had indicated a possible return to the region at the end of this week.