A 64-year-old woman with head injuries and a seven-year-old boy with fractures were taken to Canberra Hospital by helicopter following the horror crash on the Burley Griffin Way on Friday morning.

Another 24 patients - adults and children aged between 10 and 14 - sustained minor injuries and were be taken to Harden hospital to be assessed by a doctor.

It is understood the group was travelling from Griffith to Sydney for a church camp on the hired bus when it came off the road.

A teenage passenger, who did not wish to be named, was trying to sleep when the crash happened.

"I heard this sound like a crash and then I thought it would go back to normal, but it didn't," she said.

"Then we stopped at the bottom of the road and I got up to check on my baby sister, she was fine but everyone was screaming. I thought it was a dream first of all, then I needed to get out because I couldn't breathe in there.

"I was speechless when I saw the bus, after we got out some of the kids just prayed."

The Harden-Murrumburrah Health Service was swamped with patients from the crash, a spokesperson for the Murrumbidgee Local Health District confirmed. They ranged from three to 69 years old.

Three of the patients were later transported to Young Hospital.

"This was a 69-year-old female who was serious but in a stable condition and a 16-year-old female in a satisfactory and stable condition," she said.

A 60-year-old man was also taken to Young in a serious but stable condition.

NSW Ambulance initially transported 24 people to Harden hospital following the crash with another two airlifted to Canberra Hospital.

However, a Murrumbidgee Local Health Service spokeswoman confirmed "two patients walked into the hospital" later in the morning.

In total 28 people were injured in the crash.

Emergency services remain at the scene, on the Burley Griffin Way west of Harden-Murrumburrah, after being called around 8.20am.

A crime scene has been established and officers from NSW Police's Major Crash Task Force were en route on Friday morning.

The male driver is assisting investigators with their inquiries, police said.

A spokesperson for NSW Ambulance confirmed four crews of paramedics had responded to the crash at the Demondrille Creek bridge.

They were joined by police from Young and firefighting personnel from Fire and Rescue NSW.

"The scene was confronting," NSW Ambulance's Superintendent Mark Gibbs said.

"Having to assess and triage a large number of patients like this is extremely challenging, paramedics had to work quickly under difficult circumstances.

"Turning up to a job like this is really difficult, often you don't know what to expect, especially when children are involved."

The bus was the only vehicle involved in the incident and is well clear of the roadway, a spokesperson for NSW Transport Management Centre said.

While impact on traffic is minimal, the centre has advised motorists allow extra travel time and exercise caution as they pass the crash site.