Williams' celebrations following Pastor Maldonado's Spanish Grand Prix victory were wrecked soon after by a fire that broke out in the team's garage.
A Williams spokesperson confirmed four personnel were injured and taken to the medical centre at Barcelona's Circuit de Catalunya, with one seriously hurt and flown on to a local hospital.
Caterham have confirmed four of their team are being treated, one with a minor hand injury and three with respiratory issues, with one from Force India receiving treatment for smoke inhalation.
The cause is as yet undetermined.
At the time the blaze started, around 90 minutes after the race had concluded with Maldonado giving Williams their first win in nearly eight years, founder Sir Frank Williams was delivering a speech to his team.
A number of photographers and cameramen were also present when it is understood an explosion occurred, sending scores of people running into the pitlane.
Reserve driver Valtteri Bottas said: "I was there when Frank was giving his speech to everyone.
"I felt an explosion from behind, somewhere from the fuel area, and everyone ran out quickly."
As the blaze rapidly took hold, gutting the garage which included Bruno Senna's car after it had been involved in an accident in the race with Mercedes' Michael Schumacher, clouds of acrid black smoke were sent billowing into the air.
Williams mechanics were joined in their battle to beat the fire by personnel from other teams, notably Caterham and Force India in the neighbouring garages, taking 20 minutes to bring it under control.
Ambulances and fire crews were soon on hand to assist, attending to the injured, while the medical helicopter was also deployed.
A Williams team spokeswoman said: "We have four people in the medical centre receiving precautionary care, and I believe one has been flown off to hospital."