The American rider suffered a dramatic fall early in the third round of the men’s semifinal after appearing to tangle with another competitor when taking a corner.
The 28-year-old Fields, who was the gold medal winner at Rio 2016 and one of the hot favorites to win in Tokyo, hit the ground hard and required medical attention before being stretchered into an ambulance.
“We will share additional updates as they become available,” added USA Cycling BMX.
Meanwhile, Niek Kimmann of the Netherlands won his country’s first Olympic gold medal in BMX Racing after an exhilarating run.
“Since the pandemic hit I’ve had one goal, one goal, and that goal was today,” said Kimmann after the win.
“I still don’t believe I have it. I’m from the Netherlands. It’s a small country. But I know other friends who have won gold medals, so I always felt like I was the one missing it.
Earlier in the week, Kimmann’s dream was almost dashed after a freak collision with an official during training. He suffered a fractured knee but was able to recover in time after resting for much of the week.
“The last weeks I’ve felt in the best shape ever. Of course there was a lot of pressure, but I was confident,” said the 25-year-ol Kimman.
“And then I hit that official and I felt like my dream was over. But luckily with painkillers that dream was still alive. I just kept believing.”
Following his win, Kimmann sent his best wishes to Fields.
“I think we all know that there are risks to our sport, but at the end of the day we just love our sport so much,” he added.
“Connor is the defending gold medalist. I haven’t seen his crash or seen the video, but I just hope he’s OK.
“I think he’s been a great ambassador for the sport, like I hope I can be as well. It’s sad that he wasn’t able to defend his gold medal.”
Kye Whyte of Great Britain took silver, while Carlos Alberto Ramirez of Colombia earned bronze.