Nairo Quintana moved into the overall lead in the Giro d'Italia after winning a controversial stage 16 with a powerful display in tricky conditions.
The Colombian's climbing abilities helped him turn a large deficit on Rigoberto Uran into a 101-second lead.
But confusion over whether the descent from the summit of the Stelvio had been neutralised because of safety fears caused chaos and anger among the teams.
Movistar's Quintana was one rider to make up time on the descent.
He then increased the gap on the final climb of the 139km race on a day where riders had to deal with snow, fog and rain as well as the legendary Gavia and the Stelvio climbs in one day for the first time.
The official Giro d'Italia Twitter account wrongly suggested the Stelvio descent had been neutralised because heavy rain had made the road even more treacherous.
Some teams also complained that the correct information had not made its way to all the race cars.
A tweet posted on the official Giro account later apologised for the earlier incorrect message.
Riding his first Giro, Quintana finished the stage eight seconds ahead of Canada's Ryder Hesjedal, with France's Pierre Rolland third.
"Since the start of the season, I think I've shown my runner-up place at the 2013 Tour de France was no fluke," said Quintana.
"In this Giro, I've encountered a few problems but I've never lost hope. The team have been right behind me and kept my confidence intact."
Omega Pharma - Quick-Step rider Uran, who started the day with a 63-second lead over the field, trailed home in ninth place, more than four minutes behind his compatriot Quintana.
Australia's Cadel Evans, who led the Giro from stage eight to 12, lost almost five minutes as he finished 10th and is now third overall, 3'21" adrift.
Wednesday's 17th stage is a 208km trek over rolling terrain from Sarnonico to Vittorio Veneto.
Stage 16 result:
1. Nairo Quintana (Col/Movistar) 4:42.35"
2. Ryder Hesjedal (Can/Garmin Sharp) +08"
3. Pierre Rolland (Fra/Europcar) +1'13"
4. Wilco Kelderman (Ned/Belkin) +3'32"
5. Domenico Pozzovivo (Ita/AG2R) +3'37"
6. Fabio Aru (Ita/Astana) +3'40"
7. Rafal Majka (Pol) Tinkoff-Saxo +4'08"
8. Sebastian Henao (Col/Team Sky) +4'11"
9. Rigoberto Uran (Col/Omega Pharma - Quick-Step)
10. Cadel Evans (Aus/BMC Racing Team) +4'48"
1. Nairo Quintana (Col/Movistar) Team 68:11'44"
2. Rigoberto Uran (Col/Omega Pharma - Quick-Step) +1'41
3. Cadel Evans (Aus/BMC Racing) +3'21"
4. Pierre Rolland (Fra/Europcar) +3'26"
5. Rafal Majka (Pol/Tinkoff-Saxo) +3'28"
6. Fabio Aru (Ita/Astana) +3'34"
7. Domenico Pozzovivo (Ita/AG2R) +3'49"
8. Wilco Kelderman (Ned/Belkin) +4'06"
9. Ryder Hesjedal (Can/Garmin) +4'16"
10. Robert Kiserlovski (Cro/Trek) +8'02"