A lorry has come off the road on the A78 road near Skelmorlie during Friday lunchtime.
Emergency vehicles have been rushing to assist at the scene.
The incident happened about a mile south of Skelmorlie.
Witness Lindsay Cameron, 39, of Wemyss Bay, said: "It was horrific. I just hope that the driver is ok.
"I heard a terrible crunching noise, like a dumper truck unloading rocks, and a hell of a loud bang.
"The wall is demolished and the lorry is on its side."
Lindsay told how she was on a bus heading towards Wemyss Bay when the crash happened.
She said: "There were two cars in front of us so I didn't see the crash, but I heard it and sounded just horrible.
"When we passed I think the driver must have still been in his cab because someone was going to his aid.
"I'm just hoping that the driver isn't seriously hurt and that it looks worse than it actually is."
Inspector Colin Convery said: "We are responding to an RTA involving an articulated lorry. The locus is approximately 1 mile south of Skelmorlie on the A78.
"At this time the road remains open - passable with care.
"The call was received by Police Scotland at around 1230hrs today.
"Officers are in attendance, including specialist road policing officers."
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