The team boss of a teenage racing driver said he feared the worst in 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.
Formula 1 drivers Jenson Button and Lewis Hamilton offered support, and an appeal has so far raised about £580,000.
Button and fellow F1 driver Max Verstappen have both donated £15,000, while Billy's former F4 rival Devlin DeFrancesco has made the biggest donation of £26,000.
A hashtag #billywhizz is being widely shared on social media.
Billy, from Charlwood, Surrey, was trapped for 90 minutes when he collided with another F4 car which appeared to have stopped on the racetrack.
He was airlifted to hospital in Nottingham and has undergone a series of operations.
Anthony Hamilton, father of F1 star Lewis - and Nicholas, who competes in motorsport in a specially-modified car due to having cerebral palsy - said they were all "heartbroken" by what happened.
However, he said there was no reason why the youngster could not have a future in motorsport.
He said: "Nicolas is extremely keen to meet Billy and say 'look, I was born with a disability but I didn't let it stop me from going motor racing'.
"There are a huge amount of positives that can come out of situations like this and Billy is going to have the support of the world when he's out of hospital."
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."
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: "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."
Donington Park is working with the UK and international governing bodies of motor sport to investigate what happened on Sunday.