Six drivers from the all-female W Series needed medical checks on Friday, with two taken to hospital for further assessment, following a heavy crash during a qualifying session on the Spa-Francorchamps track in Belgium.
British drivers Sarah Moore and Abbie Eaton, Spain's Belen Garcia, Beitske Visser of the Netherlands, Norwegian Ayla Agren, and Fabienne Wohlwend of Liechtenstein were in the crash that happened at the notorious Eau Rouge section of the 7-kilometer (4.3-mile) circuit.
Qualifying took place shortly after the end of the second practice session for Formula One's Belgian Grand Prix on the same track.
"All drivers involved in the incident are undergoing medical assessment and two of the drivers -- Ayla Agren and Beitske Visser -- have been transferred to hospital for further checks,'' the W Series tweeted. "Thank you for your support and well wishes during that qualifying session.''
After two cars bounced off a tire wall, another car approaching them flew backwards into the back of them. One car flipped up in the air and speared the tire wall with its front nose after being pierced by another vehicle.
A sixth car following them lost control and slid to the right but avoided any contact with the others.
Qualifying resumed and defending champion Jamie Chadwick took pole position.
Several F1 drivers had trouble with grip in their practice sessions, with Ferrari's Charles Leclerc and Red Bull's Max Verstappen both going off into the barriers.
Two years ago, French driver Anthoine Hubert was killed on the same track following a high-speed crash in a Formula Two race as drivers also accelerated uphill to Eau Rouge.
The 22-year-old Hubert, who raced for the British-owned Arden team, died after an estimated 160 mph (257 kph) collision with 20-year-old U.S. driver Juan-Manuel Correa, who sustained serious injuries and was induced into a coma.
Earlier this month, there was a serious crash at the track during the Spa 24 Hours with drivers Jack Aitken and Davide Rigon needing hospital treatment.
The W Series is in its second season.
This year it is being showcased alongside eight Formula One races.
No female driver has competed in a F1 race since Lella Lombardi in 1976. Susie Wolff was the last woman to take part in an F1 weekend when she drove in a practice session for Williams at the British GP in 2015.