Officers are still trying to trace two motorcyclists who went to the aid of a man believed to be missing grandfather Gordon Wilson.
It has now been four weeks since Mr Wilson, 82, went missing from his home in Leaden Roding on Sunday, October 25.
His bus pass is confirmed as being used to board the number 352 First Bus service at Chelmsford Bus Station at 12.30pm that day.
It finished its route in Halstead and the driver believes a man fitting Mr Wilson’s description got off at the final stop at 1.30pm and walked in the direction of Butler Road.
Police received information that he was then believed to have been seen in Halstead Road, Sible Hedingham, sometime between 2pm and 4pm.
Two motorcyclists and a pedestrian had stopped to help the man, who had fallen over.
However he refused their help and continued walking in the direction of the village.
The bikers, both men, wore grey crash helmets, dark leathers and rode dark grey or silver sports bikes.
Braintree district commander Chief Insp Richard Melton said: “It is possible they were attending a motocross event in the village that day, however despite extensive enquiries, we have still been unable to trace them.
“We are keen to speak to them as they may have information that can help assist our search for Mr Wilson.
“It is now a month since he went missing and as time goes on, we are clearly growing more concerned for him.
“We are continuing our searches in the Sible Hedingham area, where he was last seen, and I would ask residents to remain vigilant and contact us with any information.”
Mr Wilson, who has a Scottish accent, is described as 5ft 11in tall and of medium build with grey thinning hair. He wears glasses and was last seen wearing a sports jacket which is either checked or navy. He usually wears a shirt, tie and jumper.
He has vascular dementia and his ill health means he can become confused and have difficulty speaking.
Mr Wilson is believed to have left home with a small amount of cash and some of his medication. He is known to enjoy long walks and had his bus pass with him.
Anyone who sees him is asked to call 101 urgently.