Real won Wednesday's first leg 2-0 but Dortmund claim they were disadvantaged by the 75-minute delay and have complained to Uefa, the European game's ruling body.
In a further potential embarrassment to Real, the Spanish media reported that Uefa and Dortmund officials had measured the goal at the other end of the Santiago Bernabeu stadium and found it to be three centimetres below the regulation height of 244cm. A Uefa Cup game between Spartak Moscow and the Swiss side Sion was replayed after a similar case earlier this season. Real were not available for comment.
The goalposts were pulled down by boisterous Real fans minutes before the scheduled kick-off and a spare set of posts had to be brought from the club's training ground.
Dortmund's president, Gerd Niebaum, labelled the game a "joke" and demanded that Uefa order a replay or award the tie to Borussia. "The players had to wait in the dressing-room, their concentration was gone and all the preparation wasted. Unlike the Spanish clubs, we are not a team that can play football at 11.30 at night," he said.
"I know how dedicated to fair play Uefa are. If we did not lodge an official protest, it would leave the door open for similar cases in the future."
If Dortmund were awarded the game as punishment against Real, they would enter the second leg on 15 April with a 3-0 lead. The goal frame was attached by supporting wires to the perimeter fencing and collapsed after members of the notorious Ultras Sur gang swung on the cables.
Real Madrid officials have been reluctant to take severe action against the Ultras Sur, but they may have to act now. The fans made Nazi gestures towards German fans and players, as they did in the quarter-final tie against another German club, Bayer Leverkusen. The behaviour continued later on the streets close to the stadium.
The Dortmund protest has taken the gloss of a Real win which stretched their unbeaten streak in European competition against German opposition to 12 matches. Their goals came from Fernando Morientes and the French international Christian Karembeu.
Whoever prevails when this semi-final is eventually settled will surely meet Juventus in the final. The Italian side gained an emphatic 4-1 win over Monaco in their semi-final first leg in Turin, with Alessandro Del Piero hitting a hat-trick.Reuse content