Filip Maciejuk (Bahrain Victorious) was disqualified from the Tour of Flanders after sparking a huge crash in the peloton.
Maciejuk was seen moving up along the side of the road with 140 km to race. He then rode into a deep grass section, lost control of his bike and swayed across the road into the peloton.
He sparked a skittle effect, with numerous riders going down.
Wout van Aert (Jumbo-Visma) was among the riders to hit the deck, although he quickly remounted and rejoined the peloton. Fellow contender Julian Alaphilippe (Soudal-QuickStep) gritted his teeth to fight the pain as he waited for mechanical service, and he was later able to chase back on.
A number of riders were left injured in the crash. Peter Sagan (TotalEnergies), the 2016 champion, was forced to abandon early in what was his final Tour of Flanders.
Race radio confirmed that Tadej Pogačar's key teammate Tim Wellens (UAE Team Emirates) was out of the race and was taken to hospital, while Ben Turner (Ineos Grenadiers) and Oier Lazkano (Movistar) also abandoned.
Other riders were left battered and bruised, including Jasper Stuyven (Trek-Segafredo).
The video referee reviewed the footage and it was soon announced that Maciejuk was disqualified, the commissaires calling the Pole to drop back and climb off his bike.
"I’m really sorry for my mistake and causing the crash today," Maciejuk said in a statement. "I hope all those involved are in good health and safe.This should not happen and was a big error in my judgement."
The peloton rode slowly the first time up the Oude Kwaremont as riders chased back on but the racing was back on on the Kortekeer climb, with 126km to race.
There were more early exits, including last year's podium finisher Valentin Madouas (Groupama-FDJ), who was sick and struggled in the opening kilometres.
Danny van Poppel (Bora-Hansgrohe) and Taco van der Hoorn (Intermarché-Wanty-Gobert) stopped after earlier crashes, while Soren Kragh Andersen (Alpecin-Deceuninck), climbed off having been ill this week and having spent lots of energy helping Mathieu van der Poel come back after being caught in an early split.
The crash was caught from the roadside and posted on social media, while Michael Rogers, the Head of Innovation at the UCI, highlighted the dangers.
