THE air and ground search for missing Ballarat man Jason Richards has been suspended as police assess their next moves.A South Australian police spokesman told The Courier this afternoon detectives were continuing to make enquiries into the case, but have stopped air and ground searches of the desert."It hasn't been called off &mdash it's just being re-assessed," the spokesman said."You've got to understand, this is like trying to find a needle in a haystack.""Enquiries are continuing, it's just we're not out there running around with a plane anymore."Click here to view the timeline of the search for Jason RichardsThis comes after the officer in charge of the search, Detective Superintendent Grant Moyle, said the search efforts have so far yielded little.Police said the trail left by Jason Richards' dog Amy has gone cold, with an aboriginal tracker tracing her path about 12 kilometres north east of where she was found on Sunday. Detective Superintendent Moyle said the tracker had been working since Tuesday to back-track the path Amy had taken before she was found south east of Glendambo. He said police had conducted extensive air searches supported by ground patrols around the Glendambo area, west to Kingoonya, south of Kingoonya, north of Glendambo, north east to Olympic Dam and south down to Woomera. "There's been a total of 4300 square kilometres searched at this point, that includes searches that were conducted very early in this investigation," he said."Unfortunately there's been no sign of Mr Richards or his vehicle during these searches, but we will continue to assess our next steps." Just three confirmed sightings of Mr Richards have been recorded on June 21 near Woomera, but there have been more than 100 unconfirmed sightings reported to police since his disappearance. He was driving a navy blue 1991 Toyota Hilux ute with a metal dog cage on the back, registered ODV 747. He was towing a trailer loaded with an aluminium boat, which was found abandoned and slightly burnt at Pimba, South Australia, on June 24.