BOSTON, Massachusetts (CNN) -- Doctors at Massachusetts General Hospital Sunday were trying to determine the cause of Sen. Edward Kennedy's seizure.
Sen. Ted Kennedy, shown in May 2007, was rushed to a hospital Saturday morning.
Medical officials said the 76-year-old Democratic icon seemed to be out of any "immediate danger."
Preliminary tests Saturday night determined Kennedy had not suffered a stroke, a physician at the hospital said.
Kennedy was flown to the hospital on a medical jet Saturday.
"Over the next couple of days, Sen. Kennedy will undergo further evaluation to determine the cause of the seizure, and a course of treatment will be determined at that time," said Dr. Larry Ronan, Kennedy's primary care physician. He added that Kennedy was "resting comfortably and watching the Red Sox game with his family." Watch what lies ahead in Kennedy's recovery »
Doctors offered no update Sunday morning.
Stephanie Cutter, a spokeswoman for the senator, on Sunday said there was no new information about his medical evaluations and tests.
"He got a good night's sleep and we expect today to be very quiet," Cutter said.
She added that Kennedy was surrounded by his family at the hospital and that he spoke with Democratic president contender Barack Obama on Sunday.
Cutter said Kennedy planned to spend the evening watching some favorite movies, including "The Great Debaters" and "Best in Show."
Cutter also said that earlier in the day, Kennedy spoke with Democratic president contender Barack Obama -- whom he has endorsed for the party's nomination.
Obama told reporters at a campaign stop in Milwaukie, Oregon, that Kennedy "sounded great, he sounded like his usual old self."
"I am just thrilled that Teddy is back on the mend," Obama said. "And I suspect he will be on the floor of the Senate immediately, doing the people's business. And there's not a better senator, or better friend, or better supporter for me than Ted Kennedy."
Well-wishers across the country sent messages to Kennedy and his family.
Senate Majority Leader Harry Reid said Saturday he spoke to the wife of the Massachusetts Democrat, Victoria Reggie Kennedy, and she told him her husband is going to be fine.
"Everyone knows he is a strong fighter," Reid said Saturday, speaking at the Nevada state Democratic Party convention.
Initially, a well-informed, prominent Democratic source in Massachusetts had told CNN that Kennedy seemed to have "symptoms of a stroke."
Someone in the Kennedy compound in Hyannisport called 911 Saturday morning, and an ambulance soon rushed Kennedy to Cape Cod hospital. Watch how paramedics' fast response time may have saved Kennedy's life »
He was then flown to Massachusetts General, where he had undergone surgery to remove a blockage in his left carotid artery in October. Kennedy's office said that blockage was discovered "as part of a routine evaluation of Sen. Kennedy's back and spine."
He suffers chronic back pain from injuries suffered in a plane crash in 1964.
In recent days Kennedy has appeared to be in fine health. On Friday, he took part in a ribbon-cutting ceremony for a new maritime learning center in New Bedford.
Family members reported that Kennedy was well enough later in the morning Saturday to call to say he would not be able to join them for lunch.
Kennedy has represented Massachusetts in the U.S. Senate since 1962. He is one of only six senators in U.S. history to serve more than 40 years. He is known as a liberal champion of social issues such as health care, family leave and the minimum wage. Take a closer look at Kennedy's life »
Kennedy, who ran unsuccessfully for the Democratic presidential nomination in 1980, is one of Sen. Barack Obama's most prominent supporters and has helped mobilize votes for him nationwide.
Obama and his presidential rivals, Sens. Hillary Clinton and John McCain, all expressed thoughts and prayers for Kennedy on Saturday.
"We are going to try to find out as quickly as possible what is going on," Obama said.
"He is one of my favorite people," he said.
McCain said in a statement he was "very sorry to hear that Sen. Kennedy has taken ill and, like millions of Americans, Cindy and I anxiously await word of his condition."
The two senators are close friends despite differing political ideologies. They co-sponsored a comprehensive immigration bill that has stalled in the Senate.
"He is a legendary lawmaker," McCain said.
Clinton said: "My thoughts and prayers are with Ted Kennedy and his family today. We all wish him well and a quick recovery."
Kennedy is the youngest of nine children in the famous family of Joseph and Rose Kennedy. His oldest brother, Joe, died in World War II; two other brothers, President John F. Kennedy and Sen. Robert Kennedy, were assassinated in the 1963 and 1968, respectively.
All About Edward M. Kennedy
|Most Viewed||Most Emailed||Top Searches|