Det Sgt Paul Olney said: “We ensured a swift and robust response to this incident and our inquiries are continuing.
“A man remains in a serious condition in hospital and our priority is establishing exactly what happened in the moments before, during and after this incident.
“His family are being supported.
“We believe there may have been a number of people passing or in the area at the time of this assault.”
He urged anyone with information to contact the force.
