The three-time world champion stayed on his bike but Poland's Rafal Majka and Italian Oscar Gatto did not.
Both riders finished the stage but the team said Majka would undergo further checks.
The 21.5-km ride around the Lido Di Camaiore was won by Mitchelton Scott, a result that put Briton Adam Yates in an excellent position to win the week-long Italian race.
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(Writing by Julien Pretot; editing by John Stonestreet)
