Klaebo was positioned side by side with four of his competitors on his way out of a turn when his ski hit American Ben Ogden.
Ogden fell, taking Klaebo and two others with him in the fall. Klaebo turned 180 degrees and hit the back of his head on the hard ice with no way to get out. His hat and glasses flew off, and he immediately grabbed his head.
Klaebo lay motionless in the snow for a long time while his competitors got on their skis. He was then attended to by the organisers, who helped him to his feet. The Norwegian left the track himself, walking, although he seemed to be very affected by the crash.
Klaebo has been taken to the hospital for tests, says TV2.no. The Norwegian camp fears that he has suffered a concussion.
"He was walking on his own and was conscious, but he had hurt himself a lot. Time will tell how it goes. He will be under observation. After that, we will have to make a status report", says national team doctor Ove Feragen to VG.no.
Klaebo obviously did not complete the semi-final, and thus his superb winning streak was broken. Before today, he had won his last 13 cross-country races, including six at the Olympics. Countryman Ansgar Evensen took the victory in the final.
If Klaebo has suffered a concussion, his successful season could be over. There is one race left on Saturday in Holmenkollen before the World Cup final in Lake Placid next weekend.