Sandy Gray, 66, left his home in Milnefield Avenue on Friday but did not return – his red Seat Ibiza car was found over the weekend in the Boat o’ Brig car park.
An RAF Helicopter from Lossiemouth has assisted in the search for Mr Gray and had been concentrated along a section of the River Spey but on Tuesday police extended that search further downstream.
Officers wearing diving masks and snorkels entered the water whenever they noted anything that could be suspicious.
Chief Inspector Willie Findlay said: “We would appeal to anybody to get in touch who may have seen Sandy in the Boat o’ Brig area or anywhere along the Speyside Way during the late morning or early afternoon on Friday.”
Mr Gray, whom police earlier described as ‘vulnerable’, is 5ft 8in tall and of medium build.