Update: Former President Jimmy Carter resting comfortably in Cleveland hospital

Former President Jimmy Carter, on a trip promoting his new book, developed an upset stomach on a flight to Cleveland and was taken to a hospital for observation, officials said.

Carter was taken to MetroHealth Hospital, where he was resting comfortably, according to the Carter Center, his Atlanta-based think tank. The center said he is expected to resume his book tour this week.

Carter, 85, was a passenger on a Delta flight from Atlanta to Cleveland when he became ill. Upon landing, he was taken off the plane by rescue crews, said Jackie Mayo, a spokeswoman at Cleveland Hopkins International Airport.

Carter is "resting comfortably" after being rushed from the airport to a hospital upon his arrival in Cleveland on Thursday morning, according to the ex-president's nonprofit organization.

"While on a flight to Cleveland, former U.S. President Jimmy Carter developed an upset stomach, and, upon arrival, was taken to Metro Health Hospital for observation," said a statement from Carter Center spokeswoman Deanna Congileo. "He is resting comfortably and is expected to resume his book tour this week."

Carter was scheduled to sign copies of his new book, "White House Diary," at Joseph-Beth Booksellers in suburban Cleveland on Tuesday afternoon, according to the store's event coordinator, Calondra McArthur. About 500 people were waiting in line at the store, he said.

In the book, Carter said he pursued an overly aggressive agenda as president that may have confused voters and alienated lawmakers. But he said the tipping points that cost him the 1980 election were the Iran hostage crisis and the Democratic primary challenge by U.S. Sen. Ted Kennedy.

Carter, a former peanut farmer elected to the White House in 1976, has spent his recent years pursuing peace and human rights, efforts that won him the Nobel Peace Prize in 2002.