Theme park bosses were informed of the accident on Tuesday at 13:57 BST but ambulance crews said the 999 call was not made until 14:08.
Alton Towers said one of its first responders was soon on the scene and security staff would have called 999 as soon as an assessment had been made.
Sixteen people were hurt, four seriously, when the Smiler crashed.
Crews from the West Midlands Ambulance Service arrived on the scene at 14:35 and they called the fire service at 14:41.
Fire crews were not initially requested by Alton Towers but the park's staff did put their own call in requesting their assistance at 14:45, the fire service said.
In a statement, Alton Towers said: "Our community first responders, based on site at Alton Towers, are trained by West Midlands Ambulance Service and form part of our security and medical teams.
"Once the incident occurred, a member of the ride staff would have called our first responders who arrived at the scene within minutes.
"After instant assessment they call our security department who then call 999 straight away."
The crash saw two carriages collide on the Â£18m ride, leaving people trapped 25ft (7.6m up) at an angle of 45 degrees for up to four-and-a-half hours.
Alton Towers said its staff built a platform to reach the injured people, although first responders initially used ladders so they could begin treating patients as soon as possible.
Joe Pugh, 18, and his girlfriend Leah Washington, 17, both from Barnsley, South Yorkshire, suffered "significant leg injuries" in the crash.
Daniel Thorpe, 27, from Buxton in Derbyshire, and 19-year-old Vicky Balch, who is believed to be from Leyland in Lancashire, were also seriously injured.
Mr Thorpe is being treated at University Hospital Coventry where his condition is described as stable.
The other three victims are being treated at Royal Stoke University Hospital.
Mr Thorpe is the assistant manager at The Izaak Walton Hotel in Dovedale.  Shura Prince, the general manager, speaking on behalf of the hotel, said they were "shocked" by what had happened.
"Dan was taking a well earned day off following a busy weekend and it's awful to hear that what should have been a relaxing and fun day has ended in horror.
"Dan is an amazing friend and colleague who I have known for many years.  Dan is hugely popular and has many close work friends.  We are like a big family at The Izaak Walton and Dan's absence whilst he recovers from this awful ordeal will leave a huge hole here.
"Our thoughts and prayers are with Dan and the other passengers at this difficult time."
A statement from University Hospital Coventry on behalf of Daniel Thorpe's family said: "We would like to thank everyone for their wishes at this time and would ask for some privacy while Daniel recovers."
1 billion
rides a year taken at fairgrounds & theme parks
1 death
in the UK since 2006/07
1.5 injuries per million rides in Europe each year
5% of accidents caused by technical problems
1 in 24m chance of being seriously hurt
Shares in Merlin Entertainments, which owns the theme park, have fallen just over 2.6% since the accident, wiping about Â£100m off its stock market value.
One analyst has estimated the park could be losing Â£500,000 for every day it stays closed.
Earlier, Alton Towers said it would remain shut on Friday while the Health and Safety Executive (HSE) continues its investigation.
A park spokesperson said anyone with pre-booked tickets would be able to visit Thorpe Park, Chessington World of Adventures, Warwick Castle or Legoland Windsor as an alternative.
Neil Craig, head of operations for HSE in the Midlands, said a specialist team of inspectors was making inquiries.
"Our role is to establish the facts," he said.
"We will want to determine that those responsible for operating this ride have done what the law requires.
"We will also ensure that if there are any lessons to be learned, they are shared as soon as possible.
"Although the investigation is in its early stages, we will take action to protect the public if we uncover evidence that could affect the safety of other rides at the park or elsewhere."
Nick Varney, chief executive of Merlin Entertainments, said the park could reopen only when the investigation had concluded but did not give a time-frame.
Friends and relatives of those injured have been offering messages of support.
Natalie Kerr, Leah Washington's form tutor at Horizon Community College in Barnsley, said it was "devastating".
"I'm sure with Leah's determination and strength she'll get through this," she said.
"Best wishes go out to her.
"Leah was one of those pupils who is so genuine, she'll do anything for you. She has a smile on her face everyday. It's devastating for everyone especially the family. She's got good family around her so she's in good hands.
"Regardless of these injuries I think she'll go on to live the life of her dreams."
The Oaks Working Men's Club in Barnsley, where Joe Pugh works as a barman, posted on Facebook: "We at the Oaks WMC would like to extend our prayers and best wishes in the speedy recovery of our barman Joe Pugh and his girlfriend Leah Washington."
Emergency services were not called until 11 minutes after the Alton Towers rollercoaster crash, it has emerged.