The race was brought to a halt as the Finn and his co-driver Timo Rautianinen were treated by medics, with Gronholm twice losing consciousness.

Ford team principal Malcolm Wilson told World Rally Radio: "At the moment they're both in the ambulance heading for Sligo, but I don't think there's any need for any major concern.

"They found some very polished tarmac and Marcus didn't get the braking he expected. He's gone into the wall with his side of the car, and it was all his side of the car that took the impact.

"He was OK initially, but then I think he passed out shortly afterwards. He came round and was OK, and then we got another phone call from Timo to say it was actually worse, that he had passed out again and was starting to lose his memory.

"Thankfully the organisers did a great job - they stopped the stage once they got the message from Timo and got the medical team there."

Gronholm holds a four-point lead over Loeb at the top of the drivers' standings going into the race - the penultimate round of this year's championship.

The crash has handed the advantage in the title race to the Frenchman, who requires victory in both rounds to claim a fourth successive world title.

"I know he'll be totally devastated about what's happened, because that's Marcus," added Wilson.

Wilson added it was too early to say whether Gronholm could return for Saturday's action - but even if he did return he would miss six stages and finish outside the points.

"We don't know at the moment," he said. "There's no real access to where the car is at the moment to see what the extent of the damage is.

"The first thing is to get the car back here, but also we need to make sure Marcus is okay and the medical team will make that decision."

Sordo holds the lead ahead of team-mate Loeb after the morning's racing.