The crash that affected about 40 riders took place with 30km to go when the peloton picked up the pace to bring back three minutes from the breakaway. Of the six Etixx-Quick-Step riders in the race, four went to the ground and were in need of medical examination at the finish, including Contreras, Gaviria, Maximiliano Richeze and Stijn Vandenbergh.
X-rays revealed that Fernando Gaviria has a fracture of the radius bone in his left arm, while Contreras, third in the general classification and the U23 leader, suffered a nasty wound to his right knee and required 15 stitches.
Richeze, the race's first leader, and Vandenbergh will line-up for the start of stage 6 despite suffering minor contusions.
An update on the condition and recovery of Contreras and Gaviria will be released in the next days, the team said.
Movistar rider Adriano Malori hit his head in the crash and was taken to hospital as a precaution. Movistar announced later that Malori will stay under observation in hospital for the next 48 hours.
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