Chloe Hosking (Ale Cipollini) eventually won the restarted stage, with Marianne Vos (WM3) finishing second and claiming the overall race lead.
Ellen van Dijk (Team Sunweb) finished third, after the race was stopped and restarted with previous leads cancelled out, according to regulations.
Jolien D'Hoore (Wiggle High5), who won the first stage, remains second in the overall standings.
Kataryzna Pawlowska (Boels-Doelmans), Mieke Kroger (Canyon SRAM), Leah Kirchmann (Team Sunweb) and Rosella Ratto (Cylance) all lost their near 30-second advantage when a river bridge opened unexpectedly in Fredrikstad.
The 140km stage between Sarpsborg and Fredrikstad had roughly 5km remaining when the bridge opened.
Race directors explained the bridge mechanism runs on a timer set in Oslo, and delays to the stage meant the action had overrun when the bridge opened.
The riders were forced to stop for a red light, with organisers restarting the race, and Hosking and Vos eventually taking full advantage.