Nine people including five children have been injured after a car overturned near a primary school today.
South Wales Police described the accident near Rhoose Primary School in the Vale of Glamorgan as "very serious".
A spokesman said: "A car has overturned near Rhoose Primary School and there are a number of casualties - including adults and children.
"The ages of those involved are not yet known. The road has been closed."
The accident happened in Fontygary Road, Rhoose, at around 8.50am as children were arriving at school.
Three rapid response vehicles and five emergency ambulances were sent to the scene, where there were "multiple casualties", a spokeswoman for Welsh Ambulance Services NHS Trust said.
She added the ambulance service was called to the single vehicle collision at about 8.55am this morning.
Glenys Watson, who works at a cafe on the same road, said the scene was "like a war zone".
"I've never seen so many police cars," she told the BBC.
Vale of Glamorgan's Tory MP Alun Cairns wrote on Twitter: "A terrible incident has taken place in Rhoose. My heart goes out to those affected. I am liaising with Police over communication and support."
It is understood there were no deaths.
A resident quoted by the BBC News website said: "Apparently the driver had a coughing fit and slammed on the accelerator instead of the brake.
"The lollipop lady was escorting a number of kids across the road at the time.
"The road is closed and air ambulances are on the way, heaps of ambulances and fire engines are at the scene."
The primary school, around five miles from the town of Barry, also has a nursery unit.
At the scene, a black Audi was on its roof on the pavement, sandwiched between a green car and a line of trees, just yards from a pelican crossing near the school.
A lollipop stick lay on the ground nearby and various pieces of clothing were strewn across the pavement.
Ian Morris, divisional manager for surgery at University Hospital of Wales in Cardiff, said: "The emergency unit at University Hospital of Wales is treating adults and children involved in the incident in Rhoose.
"The unit has specialist procedures in place for dealing with serious incidents and those have been activated to care for those involved.
"The priority now is treating those involved and supporting their families. Further information will be available shortly."
Five children and four adults, thought to include a lollipop lady, were taken by land ambulances to hospital following the incident, a Welsh Ambulance service spokesman said later.
Four children with head and/or abdomen injuries and two adults with fractures were taken to the University Hospital of Wales in Cardiff, while two adults and another child, all with minor injuries, were taken to the Princess of Wales Hospital, he added.
The spokesman said: "We were called at 08.55hrs to an RTC on Fontygarry Road, Rhoose, Barry, where a car had been in collision with several adults and children... and soon after it was declared a major incident due to the number of casualties involved and their injuries.
"We sent two rapid response vehicles, four emergency ambulances, a basics doctor, the Hazardous Area Response Team (Hart) and the Helimed helicopter to the scene.
"Six patients have been conveyed to UHW Cardiff by land ambulances - no ages or genders recorded. (Four children with head/abdomen injuries and fractures, two adults with fractures).
"There are no details regarding the severity of the injuries.
"Three patients have been conveyed to Princess of Wales Hospital by land ambulances - no ages or genders recorded. (two adults and one child - all with minor injuries)."
Mr Cairns said some of those involved had "significant" injuries, but were "not believed to be life threatening".
He said it appeared the accident was caused when a "local resident lost control" of their vehicle.
He said: "There are no fatalities, that's the important message at the moment. It's being treated as an accident, not anything malicious."
Speaking in Westminster, the MP, who will be returning to his constituency later today, said he had been in contact with the school and the police officer in charge of the incident.
"I will do everything I can to support the families of the children involved," he said.
It was "without question" that the incident would have a major impact on the village community.
"All the children will be local residents, it's a local village primary," he said.