As doctors tried to figure out why the 84-year-old former U. S. first lady hasn't been feeling well, Barbara Bush remained hospitalized in Houston on Monday.

Former President George H. W. Bush drove her to Methodist Hospital where she was admitted Saturday morning. Barbara Bush hadn't been feeling well for about a week, a spokeswoman for the Bush family told Houston's KTRK-TV.

Officials are calling the tests routine but haven't disclosed what they are for, the TV station said.

A year ago, Bush had aortic valve replacement surgery and in late 2008 she had surgery for a perforated ulcer.

The former first lady should be released within a couple of days, Bush family spokesman Jim McGrath said. (With Inputs from Agencies)