ROUBAIX, France (AFP) — Late Sunday night, Michael Goolaerts, 23, died after a cardiac arrest during the Paris-Roubaix race, his Veranda’s Willems-Crelan team confirmed.

Goolaerts was airlifted to the hospital after being knocked unconscious in a heavy crash at Paris-Roubaix on Sunday, emergency services said. Goolaerts’s crash was not seen by television cameras, but when a chase group rode by, he was seen lying on his back on the side of the road. It appeared he had crashed alone.

The Belgian was unconscious and not breathing when he was treated by the race’s medical team, then firemen and finally an emergency mobile medical outfit, the fire brigade said. He was said to be in a serious condition when he was taken to the hospital in Lille by helicopter. Goolaerts crashed with about 150 kilometers remaining in the race and was navigating one of the cobblestone sectors at the time of his crash.

After the race, Goolaerts’s Veranda’s Willems-Crelan team posted on Twitter, “No update on Michael Goolaerts yet. We kindly ask to refrain from speculation as we wait for an update on his situation. Our thoughts are with his family and friends now. Thank you for the kind messages.”

He had been a key domestique for cyclocross world champion Wout van Aert through his inaugural spring classics campaign. Van Aert finished 13th on Sunday, in the second chase group that finished 2:31 behind winner Peter Sagan (Bora-Hansgrohe).