The team boss of a teenage racing driver said he feared the worst in the aftermath of the crash which cost him his legs.
Billy Monger, 17, was in a high-speed crash at Donington Park on Sunday and later had both legs amputated.
Steven Hunter, head of Billy's team JHR Developments, said it had been a "heart-wrenching" time.
Jenson Button and Lewis Hamilton offered support, and an appeal has so far raised more than £500,000.Image copyright Jakob Ebrey Photography Image caption Billy has been described as a "huge character" by his team
Formula 1 driver Jenson Button has donated £15,000 and a hashtag, #billywhizz, is being widely shared on social media.
Billy, from Charlwood, Surrey, was trapped for 90 minutes when he collided with another Formula 4 car which appeared to have stopped on the racetrack.
He was airlifted to hospital in Nottingham and has undergone a series of operations.
Mr Hunter said Billy, who has been with the team for four years, was a "huge character" and "part of this team's racing family".
"He is an outstanding driver and a big part of what we do here. Yesterday we lined everyone up and just took some time to wish him well."Image copyright Jakob Ebrey Image caption Medical staff worked "miracles" said the head of the teenager's racing team
Mr Hunter said the moments after the crash were the worst.
"We saw the crash and our fears were as low as they could be, but all credit to the medical staff at the track and at the hospital, they have worked miracles.
"It has been heart-wrenching but from where we were after the crash to where we are now, everything has been in the right direction since.
"The pipes are out of his mouth and he spoke. He was hoarse but he just about spoke."Image copyright Getty Images Image caption Billy Monger's case has prompted support from the global motorsport community
A JustGiving page was launched on Wednesday when the extent of Billy's injuries became clear.
Mr Hunter said: "It is a testament to the world of motorsport that so many people have come forward to help."
Mercedes driver Hamilton, who has 4.32 million followers on Twitter, tweeted about Billy: "I have only just seen the news of this tragic incident."Image copyright Justgiving Image caption Jenson Button has donated £15,000 to the appeal
He later added: "Thoughts and prayers are with you and your family, @BillyMonger."
Button wrote on his Instagram account: "Hey guys this fellow racer Billy Monger had a big shunt this past weekend at Donington and sadly Billy has had amputations to both legs.
"This guy needs our help so if you can please donate, I will be doing as much as I can to help this dude out."