WASHINGTON — Sen. Edward M. Kennedy, D-Mass., battling a brain tumor, became ill at a post-inauguration luncheon for President Barack Obama on Tuesday and was taken by ambulance to a hospital.< There was no immediate word from medical personnel on his condition.< “It looked like a seizure,” said Sen. Orrin Hatch, R-Utah, who said he was with Kennedy until they reached the ambulance.< Kennedy, 76, had appeared in good health and spirits hours earlier when he stepped out of the Capitol and onto the inauguration platform where Obama took the oath of office.< Sen. Robert C. Byrd, 91, also was taken from the luncheon but it was not clear whether his departure was prompted by his health.< Kennedy has suffered seizures since he was stricken and had surgery for his tumor last year, but it was not known what caused him to fall ill at the early afternoon lunch.< Former Vice President Walter F. Mondale said Kennedy was swapping stories with others at their table when “something happened. I don’t know what it was, he just stopped.”< “It was really kind of a shock to us all,” he added.< Sen. Jay Rockefeller, D-W., Va., told reporters the president rushed over to Kennedy’s side.< “There was a call for silence throughout the room,” he said. “The president went over immediately. The lights went down, just to reduce the heat, I think.”< In his remarks, Obama said his prayers were with the stricken senator, his family and wife, Vicki.< “He was there when the Voting Rights Act passed, along with John Lewis who was a warrior for justice.< “And so I would be lying to you if I did not say that right now a part of me is with him. And I think that’s true for all of us,” Obama said.<