NEW YORK — A giant balloon in the Macy's Thanksgiving Day parade, swinging out of control in sudden bursts of wind, struck a light pole Thursday in Times Square, injuring two spectators and scaring scores of others in an eerie replay of a 1997 accident that had prompted pledges of safety reforms.

The M & M balloon, a 515-pound, polyurethane contraption filled with 13,335 cubic feet of helium, began to list erratically about 11:40 a.m. as it entered Times Square, witnesses said, before it crashed into a lamppost and was punctured. As the balloon collapsed, it pulled off a light fixture, which crashed to the ground amid a small sea of spectators.

Police and emergency workers descended on the scene, at one of the signature points of the

81-year-old parade, and the victims — a

26-year-old woman, who was using a wheelchair, and her 11-year-old sister — were taken to Bellevue Hospital Center, where they were treated for cuts and bruises.

The girl, identified by officials as Sarah Chamberlain of Albany, was cut in the back of the head, received six stitches and had a chipped tooth; her older sister, Mary, with a bruised forehead, was given a CAT scan, officials said. Both were released several hours later.

The balloons had been sent afloat at 9 a.m. by city and parade officials confident that the day's winds were milder than feared. Witnesses in Times Square said several balloons had veered and tilted as their handlers appeared to struggle through the open area of Times Square. One spectator said another balloon had bumped the same light pole earlier.

As the M & M balloon moved down Broadway, toward West 43rd Street, the wind sent it eastward into an office tower at 1500 Broadway. As dozens of volunteer handlers tried to redirect the balloon on its proper path, it veered into the light pole anchored on a traffic island.

"It looked like it was happening in slow motion," said William Dowling, 35.

, a Manhattan native who had recently moved to Fredericksburg, Va. "It was like a frozen moment with everyone just looking up. It's amazing no one else was hurt." His wife, Rebecca Dowling, 27, said the entire crowd gasped. "There was this collective scream," she said.

The episode was a bizarre repetition of one eight years ago. On Nov. 27, 1997, a six-story-tall Cat in the Hat balloon in the parade slammed into a cast-steel lamppost at 72nd Street and Central Park West, shearing off a horizontal arm and injuring four people, one of whom spent 24 days in a coma.

That accident had led to a mayoral task force and promises by Macy's of, among other things, more training for its balloon handlers. In recent days, with forecasts of strong winds, Macy's officials had said that the enhanced training was still in effect. But they conceded that hundreds of handlers who would be working underneath the enormous balloons had received no field training, only instructional materials and brief orientations before the parade.

Mayor Michael R. Bloomberg, at a news conference in Times Square roughly an hour after the accident, said that an investigation was under way. He suggested that the handlers of the balloon might have "overcorrected" after a gust blew the balloon eastward.

The M & M balloon was removed immediately after the accident, but police and other officials allowed the parade to complete its 2.5-mile route to Herald Square, saying the damaged balloon was one of the final attractions in the three-hour event.

Robin B. Hall, the Macy's parade director, said the M & M balloon was controlled by 48 or 50 balloon handlers, under the direction of a 12-member "flight" team, including a highly experienced pilot.

Only four of the handlers had not worked in a previous parade, he said. Macy's officials would not make any of the handlers or flight directors available for interviews. The M & M balloon was making only its second appearance in the parade.

The light pole was one of dozens that were replaced, at Macy's expense, after the 1997 accident. The change was intended to make the light poles less susceptible to being snagged by the balloon ropes. The light pole in the 1997 accident had a horizontal arm; the light pole Thursday had two fixtures suspended from arms turned downward on either side of the pole.

"Whether the light fixture was properly secured — we will find that out as part of our investigation," Bloomberg said. The light fixture consists of a metal base, a bulb and a translucent lens and weighs about 30 pounds.

The mayor promised a review of parade operations. "We have to take a look and see what procedures we want to change, if any, before the parade next year," he said. "But it's something that at this point appears to have been an accident and fortunately, the injuries do not appear to be life-threatening or serious."

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Six months after the 1997 accident, a 12-member panel appointed by Mayor Rudolph W. Giuliani had recommended restrictions on the operation and size of the balloons, and tighter city regulation of several aspects of the parade. The M & M balloon, which depicts two candy characters aboard a hot-air balloon, was 40 feet long, 30.5 feet wide and 50.5 feet tall.

The rules prohibit giant balloons from being operated in sustained winds exceeding 23 miles per hour or wind gusts exceeding 34 miles per hour. At noon Thursday, the winds in Central Park were measured at 13 miles per hour, with gusts up to 20 miles per hour, according to the National Weather Service's forecasting office in Upton, N.Y.

The 1998 rules directed the city's Department of Transportation to approve the construction and operation of the balloons and the training of balloon handling volunteers.

Its commissioner, Iris Weinshall, said Thursday that the department had certified the M & M balloon, which was built at the Macy's Parade Studio in Hoboken, N.J., as safe to operate.

The rules also called for a police officer to accompany each large balloon, a recommendation that Police Commissioner Raymond W. Kelly said was followed Thursday.

The official investigation may well focus on training requirements, which several volunteers said were not stringent.

Anne Kelly, 57, of Mountain Lakes, N.J., a first-time volunteer who helped handle the Jojo's circus girl balloon, said she had missed two voluntary training sessions at the Meadowlands arena but had read instructions on balloon handling provided by Macy's and had listened to directions from other balloon handlers, a captain and a pilot. "I didn't feel unprepared," she said.

The accident put a damper on an otherwise smooth parade, which began in 1924 and now attracts about 2.5 million spectators. The procession — 14 giant balloons, 37 smaller balloons, 27 floats and 10 high school marching bands — slowly made its way down Central Park West from 77th Street. The weather was brisk and clear. An early morning rain had ended at 6:53 a.m.

After the parade passed Columbus Circle and curved onto Broadway, the wind began to buffet some balloons back and forth. A medium-size Uncle Sam balloon took a nosedive to within 4 or 5 feet off the ground near 57th Street. A giant Ronald McDonald balloon also dipped precipitously.

Minutes later, the M & M balloon entered Times Square.