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Tom Smart, Deseret News
as Brigham Young University and Saint Mary's play men's basketball Saturday, Jan. 28, 2012, in Provo, Utah.

PROVO — No. 21 Saint Mary's built a 23-point second-half lead and held on for a 80-66 victory over BYU Saturday at the Marriott Center.

It marked the Cougars' second consecutive loss at home.

BYU trailed by 12, 40-28, at halftime, then the Gaels extended their lead to 17 early in the second half after Matthew Dellavedova drew a questionable foul that prompted at least one fan to throw debris onto the floor. The officials called a technical foul on the crowd, and Dellavedova knocked down both free throws. Moments later, Jorden Page drilled a 3-pointer.

Suddenly, the Gaels led, 45-28.

Things would only get worse for the Cougars, as Saint Mary's went up by as many as 23 points, 55-32.

BYU whittled that 23-point deficit to nine with just under four minutes remaining, but couldn't get any closer.

Frustrated Cougar fans threw debris after the final horn, littering the court.

The Gaels' Brad Waldow scored a game-high 19 points while Clint Steindl scored 16, including 14 in the first half.

For BYU, Noah Hartsock and Matt Carlino each had 15 points and Brandon Davies added 14.

The Cougars shot just 41 percent from the floor, compared to 56 percent for Saint Mary's. BYU made only 2-of-13 3-point attempts.