BOSTON — Doctors treating Teresa Heinz Kerry, the wife of U.S. Secretary of State John Kerry, have ruled out several serious conditions such as a brain tumor, stroke or heart attack as possible causes of the seizure-like symptoms she experienced, a spokesman for Kerry said Tuesday.

Heinz Kerry, 74, was flown to Massachusetts General Hospital after becoming ill Sunday on the Massachusetts island of Nantucket, where the couple owns a home.

Her condition continues to improve and she remained in fair condition at the hospital, State Department spokesman Glen Johnson said in a statement. While evaluations continued to determine what caused the seizure-like symptoms, Johnson said she, her husband and other family members were “deeply grateful” to learn that doctors had eliminated a brain tumor, stroke or heart attack as possible triggers.

The positive developments would also enable Kerry to temporarily resume his official schedule. Kerry will “briefly travel” to Washington on Tuesday to open scheduled meetings between the U.S. and China on strategic and economic issues.

“Members of the family will remain at the hospital before the Secretary’s return to Boston,” Johnson said.

The family did not plan to release any further information about Heinz Kerry’s condition until she was discharged from the hospital, he added.

Heinz Kerry, an heir to the Heinz ketchup fortune, is the widow of former U.S. Sen. John Heinz, who was killed along with six others in 1991 when a helicopter collided with a plane over a schoolyard in Merion, Pa. She married Kerry, a longtime senator from Massachusetts, in 1995.

In 2009, Heinz Kerry was diagnosed with breast cancer and underwent lumpectomies on both breasts.

Kerry, the 2004 Democratic presidential nominee, resigned from the U.S. Senate on Feb. 1 after being confirmed to succeed Hillary Rodham Clinton as Secretary of State.

Johnson said the family was humbled and overwhelmed by the outpouring of support for Heinz Kerry and well wishes that had poured in over the past several days, including those from former congressional colleagues and staff. The family was also touched by several messages and phone calls received from foreign leaders, he said.