A crash involving one vehicle caused one of Scotland's major motorways to be shut for nearly two-and-a-half hours, causing tailbacks of up to 20 miles and traffic misery for hundreds of motorists stuck in high temperatures.

The hot weather also took 
its toll in Edinburgh, where firefighters tackled a grass fire on Arthur's Seat.

Police closed both carriageways of the M90 between Junctions 3 and 4 near Dunfermline at around 5pm yesterday as one of the casualties had to be airlifted to hospital having escaped the burning car.

Police Scotland said a white Fiat Punto car rolled over and a 20-year-old woman and a 21-year-old man were injured, but they were unable to say how seriously.

The decision to shut Britain's most northerly motorway, which runs from the Forth Road Bridge to Perth, came as motorists started leaving Muirfield in East Lothian at the end of the Open.

The northbound carriageway was eventually open two-and-a-half hours later while the southbound route remained shut last night with no estimate on how long it would take for it to re-open.

Drivers were reported to have been stuck on the motorway for more than three hours.

Some talked of their frustration at having to wait in hot cars for hours with children as they scrambled to find information.

Half an hour after the crash, Police Scotland would only confirm there was a serious 
incident near Dunfermline.

A spokesman for Traffic Scotland later said police were "in the process of turning vehicles stuck within the closure and getting them off the carriageway".

Later police confirmed there had been a crash but said they were not aware of how serious the injuries were.

A police spokesman said: "The vehicle went out of control and spun. There were two occupants in the vehicle who have both been taken to hospital. We don't know if they were seriously injured. One was airlifted by helicopter. We are not sure of their condition.

"We are carrying out investigations at the scene and hope to have the whole road open as quickly as we can. It was initially closed in both directions but the northbound carriageway was later re-opened.

"Both occupants managed to get out the car themselves, but information is fairly sketchy – whether they walked or were thrown out we are not sure."

The spokesman said the 
motorway had to be closed to allow the helicopter to land.

A police spokesman said: "Some of the traffic had to be re-routed on to the other side of the carriageway, and back up to an off road just to clear the area. Because the helicopter had to land on the motorway, you need to clear both sides."

It came just two days after a crash involving a Vauxhall Corsa, which struck the central reservation near the same spot of the M90, closed one lane of the southbound carriageway and caused delays. The driver was uninjured.

Meanwhile, firefighters were forced to stop tackling a grass fire on Arthur's Seat in Edinburgh after winds whipped up 20ft flames.

More than 100 calls were received after the blaze began at about 4.40pm, the fire service said.

About 22 crew were involved 
in trying to extinguish the fire, which broke out about half a mile up the hill and covered an area spanning 200m by 100m.

Efforts to stop the flames were suspended after winds caused them to leap 20ft, a spokeswoman said. It is not yet known how the fire started, although there have been several warnings about wildfires because of the hot weather in recent days. Weather forecasters said Britain could turn tropical today with high humidity and the hottest day of the year so far before violent thunderstorms bring a dramatic end to the heatwave.

The UK has seen its longest prolonged heatwave in seven years, although temperatures dipped slightly over the weekend.

Today it is expected to be 23C 
in Glasgow, 21C in Inverness and 18C in Edinburgh.