They warned that Geoffrey William Dudgeon, 35, who is on the run from Stocken prison, Leicester, has a history of violence and is thought to be 'armed and very dangerous'.
The security guard, James Doy, was shot dead last week when he was on night duty at the firm of J G Osborne, in Ginhouse Lane, Rotherham. A lorry and pounds 5,000 cash were stolen. Mr Doy, 55, was shot several times and his body left under a tree in the firm's compound.
The stolen Volvo articulated lorry was later found on fire in Leicester.
Det Supt Derek Smith, leading the investigation, said every aspect of the lorry's recent history was being investigated. It had just returned from a trip to Spain with a load of fruit which had been delivered to Glasgow on the day of the murder.
The lorry had then been taken back to Rotherham ready for a journey to Italy next day. Police have been checking a theory that there may have been a drugs connection because of the lorry's movements on the Continent.
Dudgeon is originally from Coventry, but is thought to have connections in Leicester, Southampton and London. He is known to travel extensively in Europe, usually hitchhiking.
He frequently calls himself 'Frank' and is also nicknamed 'Crusher'. He is described as 5ft 8in tall, stocky, with brown hair, a droopy moustache and tattoos on his legs, arms and chest.Reuse content