The NFL has blamed an error by a clock operator, and the failure to correct it by on-field officials, for an unusual run-off of 18 seconds near the end of the Pittsburgh Steelers' 24-20 victory Monday night over the San Diego Chargers.

The performance of those responsible will be reviewed as per standard procedure, according to league spokesman Michael Signora.

The incident occurred after a touchback as the Steelers gained possession for their game-winning drive late in the fourth quarter. By NFL rule, the clock should not have started because the receiving team possessed the ball in the end zone without taking it onto the field of play.

The clock continued to run, however, and when the Steelers huddled, the clock showed 2:38 remaining instead of 2:56, as it should have.

Official game time is kept on the stadium scoreboard, which is operated by a league-hired local resident who usually has college football officiating experience.