The story

Sen. Ted Kennedy was undergoing more tests Monday as doctors tried to figure out what caused his seizure.

"[It's] unclear if we'll know anything conclusive later today or tomorrow," spokeswoman Stephanie Cutter said Monday. "As of right now, I expect him to stay again tonight."

The 76-year-old Democratic icon was flown to the hospital after having a seizure Saturday. Read full article »

CNN's Deb Feyerick contributed to this story.

All About Edward M. Kennedy