The Cubs said Crawford wasn't feeling well and was taken to Advocate Illinois Masonic Medical Center. The team had no further information and a woman identifying herself as Crawford's nurse late Tuesday night said he "wished to have no comment."
Crawford, the crew chief, was seen talking with Cubs trainer Mark O'Neal and another umpire near the dugout before the top of the third inning. They then headed down the steps, and the teams were called off the field.
They went with a three-man crew when play resumed 13 minutes later. Paul Nauert moved from first base to the plate, Tom Hallion went from second to first, and Brian O'Nora stayed at third.
The 60-year-old Crawford has a history of health problems, particularly a bad back.
He missed a game between the Indians and Rays last Aug. 18. Three days earlier, Crawford worked 3½ innings of an Astros-Dodgers game before leaving. Crawford wouldn't disclose why he left, but then-Houston manager Phil Garner said it was a back problem.
Crawford also missed a game between the Pirates and Mariners last June because he was ill, as well as a pair of games last May because of "health issues."
It also wasn't the first time Crawford left a game at Wrigley Field.
He left in the fourth inning Game 1 of the 2003 NLCS between the Cubs and Florida after falling ill.