Heavy rain resulted in dangerous conditions and meant that the majority of the 171-kilometres ride from Atripalda to Salerno was at a steady pace.

Groves edged himself in front on a crowded home straight to clock the winning time of 4hour 30min 19sec for his first stage victory at the Giro.

He was followed by Italy's Jonathan Milan, who now leads the points classification, and Denmark's Mads Pedersen.

The first crash, at the 19km mark, was not caused by the weather as a stray dog ran across Italian Davide Ballerini causing him and Soudal-Quick-Step team-mate Evenepoel to come off their bikes.

The pair were tended to by the race doctor and eventually re-joined the racing.

A further three crashes followed in the final 10km as riders prepared for the mass sprint finish.

Groves was caught up in a fall on the final bend with 7km to go alongside general classification leader Andreas Leknessund of Norway and Slovenia's Primož Roglič, who is 30 seconds away from the overall lead.

Evenepoel, who wore the maglia rosa for the first four stages, then went down for a second time with 2km remaining.

He was visibly furious as he got back onto his bike and appeared to suggest another rider caused the crash by cutting across his path.

The final collision came at the very end of the stage. 

Cavendish went on the attack but his wheel slipped during the move and as he struggled to stay upright he nudged into Italian duo Alberto Dainese and Filippo Fiorelli.

He then went careering across the road before falling off his bike and sliding across the finish line.

Stage six is due to begin tomorrow with a 156km loop beginning and ending in Naples.