It was during the qualifiers on the classic course Spa-Francorchamps that the accident occurred.
Several cars lost their grip in a fast curve and crashed into each other.
A total of six drivers were involved.
British Sarah Moore was first into the curve.
- I saw that it started to drizzle.
As the rain was coming, it was the last chance to warm up the tires on the dry track, she says in a video.
- So I had to invest everything.
I dropped the bracket and after that I was just a passenger.
According to the W Series twitter account, two drivers - Ayla Agren and Beitske Visser - were taken to hospital.
All involved are said to be fine under the circumstances.
- I feel a little sore. But I'm thankful that all drivers are okay, says Moore.