FARGO, N.D. (AP)—Marcus Williams returned an interception 98 yards for a touchdown to help North Dakota State blow open a close game Saturday and explode past Youngstown State 48-7 in a matchup of highly regarded Football Championship Subdivision teams.

Williams stepped in front of a Kurt Hess pass at the NDSU 2 midway through the second quarter as the Penguins were driving for a possible tying score. Instead, it made the score 21-7 and the Bison tacked on two more touchdowns on the stunned visitors before halftime to take a 35-7 lead.

"Anytime the quarterback throws a pick-six, that's really hard for a quarterback to overcome," NDSU coach Craig Bohl said of the interception. "I thought it was a great play by Marcus."

The Bison (5-0, 2-0 Missouri Valley) also returned a punt for a touchdown when Ryan Smith zigzagged through the middle of the field for a 76-yard score in the third quarter. That made it 45-7.

Brock Jensen passed for 200 yards and two touchdowns and John Crockett ran for 103 yards and two scores for NDSU. The Bison defense forced three turnovers in the first half, including a fumble on the first play from scrimmage that was recovered by Christian Dudzik.

"We came out of the gate hot, just like we wanted to," Jensen said. "We know how good of a football team we can be if we play clean football."

NDSU has played turnover-free football in 11 of 20 games since losing to Eastern Washington in the quarterfinals of the 2010 playoffs.

The Penguins (4-1, 1-1) had enjoyed success against NDSU, coming in with a 4-2 series advantage and a 2-0 record at the Fargodome. They handed the defending FCS champions their only loss last season. Youngstown also had last week off to prepare for the game.

"It's obviously very disappointing," Youngtown coach Eric Wolford said. "It's one game, though."

Hess, a first-team all-conference selection last year, came into the game leading all FCS quarterbacks in passing efficiency. He had completed 55 of 83 passes for 765 yards, with eight touchdowns and no interceptions.

Hess finished with 11 completions in 20 attempts for 117 yards and two interceptions. Bohl said the Bison took him out of his comfort zone.

"Anytime you can harass the quarterback with your defensive line, that can create problems," Wolford said. "But we let this game get out of control very early on because of self-inflicted turnovers."

Linebacker Grant Olson, who led the Bison defense with 12 tackles, pointed to the Williams interception return as the key play.

"That was a 14-point swing. It would have been a different game without that," Olson said. "We didn't look back from there."

The game was played before a record crowd of 19,065 at Gate City Bank Field at the Fargodome.