On February 15, 2001, about 1516 hours Pacific standard time, a Cessna 172N, N4922D, veered off the runway and collided with a taxiway sign during landing rollout on runway 28L at the Montgomery Field, San Diego, California. The airplane was substantially damaged. Neither the airline transport certificated pilot nor passenger was injured. Plus One Flyers, Inc., San Diego, operated the airplane. Visual meteorological conditions prevailed, and an instrument flight rules flight plan was filed. The personal flight was performed under 14 CFR Part 91, and originated in Scottsdale, Arizona, about 1235 mountain standard time. Airport personnel reported that the collision occurred about 1,000 feet upwind of the runway's threshold. The airplane impacted the taxiway "C" sign and veered off the runway. The airplane came to a stop about 550 feet farther upwind of the sign and about 200 feet north of the runway. The pilot stated to the National Transportation Safety Board investigator that during the landing rollout, as the airplane was decelerating through about 50 knots, the left wing suddenly lifted up. Thereafter, he lost control of the airplane. He additionally reported that he was unaware of the reason for this occurrence. No mechanical malfunctions were reported with the airplane. In the pilot's partially completed accident report, he indicated that when the airplane was "almost half way down the runway" the left wing rose up, and thereafter he lost control of the airplane as it "violently" veered off the runway. The pilot also reported that when he was on final approach the tower controller reported that the wind was from 270 degrees at 6 knots.