TRONDHEIM, Norway - Norway's ski jumping team deliberately cheated by using manipulated jumpsuits at the Nordic World Ski Championships, where two of their competitors were disqualified during Saturday's ski jumping event, the Norwegian Ski Federation said on Sunday.

Marius Lindvik and Johann Andre Forfang were disqualified from the men's large hill competition, while Joergen Graabak was also disqualified from Friday's Nordic Combined team event, but this was related to his bindings.

"The support system has explained that on Friday, they chose to put a reinforced thread in the jumpsuit of Forfang and Lindvik," Norway Ski Federation general manager Jan-Erik Aalbu told a press conference.

"This was done knowing that this is not within the regulations, but with a belief that it would not be discovered by FIS's equipment controller.

"The way I consider this. We have cheated. We have tried to cheat the system. That is unacceptable."

Lindvik had finished second but was denied the silver medal following his disqualification after an equipment inspection, along with compatriot Forfang who had finished fourth.

Race director Sandro Pertile said afterwards that they had received information prior to the event about possible manipulations of the suits, and had also received an official protest from three nations.

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The organizers found nothing untoward during the initial check, but after the race they discovered different material in the seams.

Earlier on Sunday, the International Ski and Snowboard Federation (FIS) said that their Independent Ethics and Compliance Office had begun an investigation into the circumstances surrounding the disqualifications.

"I welcome the fact that FIS is now also opening an investigation. And of course, we will cooperate fully with them," Aalbu said.

Lindvik had earlier won gold in the normal hill event, and was also part of the mixed team which won the large hill while the Norwegian women won the normal hill. Aalbu said their cheating was related only to Saturday's event.

"There is no indication that this form of manipulation has been used earlier in the season, or in this championship," he said.

"I have been working again with the support system last night and throughout the day, that this was only, if you can use that word, two suits. Saturday's competition, and nothing earlier in the championship.

"I would like to use the situation to underline the seriousness of this matter. We have cheated.

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"I would therefore like to apologize on behalf of the ski jumping camp to the other nations, the audience, everyone who has met at the arena, FIS and to the organizers."