Two women died and 48 people were injured when a coach careered into a hedge and struck a wall in Cornwall.
The coach crashed at Morval, on a steep and winding hill on the approach to the seaside town of Looe.
Eight passengers, who were on an Age Concern trip from Exmouth, Devon have been taken to hospital. They are believed to be critically injured.
Police said the 57-year-old coach driver had been arrested on suspicion of causing death by dangerous driving.
One woman died at the scene while a second woman was pronounced dead on arrival at Derriford Hospital in Plymouth, the Devon and Cornwall force said.
Passengers who were not seriously injured were assessed by medics at the scene before returning later to Exmouth to tearful reunions with relatives.
All 50 passengers are believed to be in their 60s or older.
Exeter-based Carmel Coaches, which owns the vehicle, said: "Carmel Coaches extends our deepest sympathies to those involved in today's accident.
"We are co-operating with the authorities in the investigation of this tragic event."
Steve Dace, of Age Concern, Exmouth, said: "It's been an absolutely dreadful day.
"It's been devastating for all concerned and a shock for staff and volunteers at Age Concern.
"We have been using the coach company involved for a number of years and they have an excellent reputation. They have done all they can to support those involved in the accident."
Terry Perring, who lives nearby, said he could see people being treated by paramedics in the road.
"The rest of the emergency services had a staging alongside the coach and were taking out the windows of the coach and the seats to extract other passengers.
"But we didn't have any idea at all what sort of injuries or anything anybody had at that time."
Tracey Chudleigh, who was one of the first motorists on the scene, said: "The passengers were very shaken. Several were coming off covered in blood.
"There was lots of broken glass around. They were very scared.
"The emergency services were brilliant. They were here so quickly."
Those who are able to walk were assessed by doctors at a nearby village hall.
Three air ambulances, two from Devon and one from Cornwall, were sent to the scene.
Two search and rescue helicopters also attended, one from RNAS Culdrose, near Helston in Cornwall, and one from RMB Chivenor, near Barnstaple in Devon.
The A387 at Morval has been closed to traffic.
Exmouth mayor John Humphreys said: "I am absolutely devastated and shocked. My heart goes out to all those involved and their families."
Ch Insp Ian Drummond-Smith, of Devon and Cornwall Police, tweeted: "My thoughts with victims & all 999 services dealing with this horrific crash in Cornwall today."
Cornwall Air Ambulance tweeted: "Our sincere condolences and thoughts are with all those involved."