Kristijan Koren sent home from Giro over potential anti-doping violation

It is a blow for Vincenzo Nibali, who is leading the team in Italy and must now attempt to win the title with a six-strong supporting cast instead of seven.

The provisional suspensions are part of Operation Aderlass, an Austrian police investigation that uncovered a blood doping ring, with the UCI now investigating the "use of prohibited method" between 2012 and 2013. Bahrain-Merida sport director Borut Bozic, who retired from racing last year, was also named in the four-man list.

"The team strictly advocates zero-tolerance doping policy and has therefore provisionally suspended both members concerned," read a statement on Bahrain-Merida's website.

"We would like to stress that both cases relate to the 2012 and/or 2013 seasons. The Team always carries out a thorough medical checks (including biological passport check) of any new signed rider."

Alessandro Petacchi and Kristijan Durasek are the others named, with Petacchi winning the points classification at all three Grand Tours. In March, Austrian duo Stefan Denifl and Georg Preidler were suspended in the same operation.

The news continues a difficult week for the sport, which saw Team UAE rider Juan Sebastian Molano removed from the Giro after internal tests gave "unusual physiological results" and Switzerland coach Danilo Hondo sacked after the German admitted he was involved in blood doping.