Lambrecht was taken to hospital in a helicopter following the crash which occurred around 96km from the end of the Chorzow to Zabrze stage, the BBC reported.
"The biggest tragedy possible that could happen to the family, friends and teammates of Bjorg has happened... rest in peace Bjorg," Belgian team Lotto Soudal said on Twitter, without providing any details of the accident.
Race organisers added: "There are no words to describe this tragedy. Bjorg passed away following an accident on today's stage. Our thoughts are with his family, friends, team and the whole cycling community."
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Lambrecht, racing in only his second season as a top level professional, was named the most promising youngster in the Criterium du Dauphine in June. (Reporting by Shrivathsa Sridhar in Bengaluru; Editing by Ken Ferris)
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