The pit lane of the Circuit de Catalunya was wreathed in acrid smoke and hastily evacuated after a flash fire broke out in the Williams garage just as the team was celebrating a famous victory in the Spanish Grand Prix.
Shortly after everyone had gathered together for a team photo to mark the occasion, team owner Sir Frank Williams was giving a short speech to the team in the garage when there was a small explosion and a fire broke out at the back of the temporary garage area.
The area engulfed by flames was near where the race fuel was stored, and it's believed that work had already underway draining unused fuel from Bruno Senna's race car in readiness for transportation to the next event in Monaco when the rig started to leak fuel.
How the fuel leaked, and what sparked the fire, is not yet clear and will be formally investigated by Spanish authorities. Initial theories suggested that a spark from the car's KERS battery might have been the imediate source of ignition.
No one was directly hurt in the immediate explosion or in the initial outbreak of flames, and everyone hastily rushed out of the garage area as it filled up with billowing black smoke. Sir Frank himself was removed to safety, and race winner Pastor Maldonado helped carry out his shocked family members to the paddock area.
In the immediate response to the fire, Williams crew grabbed fire extinguishers and attempted to tackle the flames, and were joined in their efforts by personnel from teams up and down pit lane rushing to their assistance and bringing further extinguishers with them. Round the back of the garage area, fire hoses were deployed.
It's believed that a number of those tackling the fire suffered from smoke inhalation, and at least one person was reported to have suffered burns to his legs after his trousers were set alight.
All those affected were removed to the infield medical centre, where a group of worried Williams personnel were seen gathered awaiting news. The medical helicopter was also dispatched, and it's understood that at least one person was taken to hospital for evaluation and treatment.
Caterham F1 - which had a garage adjoining that of Williams in Barcelona - issued a statement which said that "four people have been taken to the circuit medical centre for examination; one with a minor hand injury and three with respiratory issues.
"A further statement will be issued when more details about the incident are confirmed," the statement added.