A prisoner knocked out a security guard and left another requiring hospital treatment during an escape from a private security firm van.

The man rendered one guard unconscious and injured another's arm before jumping from a G4S van while he was being returned to prison from a visit to St John's Hospital in Livingston, West Lothian.

The two G4S staff are now in hospital being treated for their injuries, which are not thought to be life-threatening.

Following the escape a major search was launched, with a helicopter called in to assist teams on the ground.

The prisoner was later named as 33-year-old Anthony Ferrie, a prisoner from HMP Addiewell, who is serving time for housebreaking offences.

Ferrie described as white, 6ft tall, of slim build and wearing a blue sweater, jeans and trainers. Police said he has links to Bellshill, Motherwell and Grangemouth.

Members of the public are advised not to approach him but to contact Police Scotland on 101.

Willie Galloway, head of operations for G4S's custody transport in Scotland, said: "During a prisoner transport movement at approximately 1pm today, a prisoner escaped custody at St John's Hospital in Livingston.

"Two members of our crew were injured during the incident which left one unconscious and the other with an injury to their arm.

"While they both remain in hospital, their injuries do not at this stage appear to be life threatening and we are supporting them and their families.

"We are assisting Police Scotland's enquiry to recapture this prisoner and are working with the Scottish Prison Service to understand the events leading up to this escape."

A spokeswoman for the Scottish Prison Service said: "We are aware that an individual has escaped from the custody of G4S while on a hospital escort.

"We are assisting Police Scotland to apprehend them."