Orienteering star Alexandersson, who also runs long-distance races in mountainous terrain, won the Mont-Blanc Marathon in June ahead of Robsahm. The race was the Norwegian's very best in trail running.
On Saturday, she died after falling about 10 metres from the top of Romsdalseggen, according to NRK, at only 30 years old.
"I have no words," Alexandersson writes on Instagram, followed by a white dove and a broken heart.
"Your smile, energy and kindness will forever remain in my heart. We will always remember you and miss you Ida!"
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