UPDATE: POLICE will use a low-flying helicopter and kayaks along the South Esk River at Perth, as the search for missing Launceston man Ben Plowright ramps up.
The date of the river search has not yet been determined.
EARLIER: POLICE are still deciding what direction to take the Ben Plowright investigation after tests on a road stain at Perth returned no trace of the missing man.
Last month, a reported sighting of the Launceston 20-year-old saw police conduct forensic tests on an unknown substance on Mill Road.
This week, Deloraine Inspector Scott Flude said the substance was not linked to Mr Plowright's disappearance.
Inspector Flude said if the results had have been positive, it likely would have seen police retrace their steps of the Perth area this week.
That will now not go ahead.
He said police would make a decision on their next move in the coming week.
Police do not suspect foul play in Mr Plowright's disappearance.
He was last seen leaving a party at Perth about 9pm on May 30, wearing a grey hoodie, jeans, bright-coloured Converse shoes and glasses.
A large-scale search of Perth in mid-June was Tasmania’s largest missing persons search in 30 years, but it returned no trace of Mr Plowright.
Tasmania Police has since seized control of his Facebook page in a bid for clues. Mr Plowright is described as 175 centimetres tall, of slim build with brown hair. He is of Thai descent.
Police urge anyone with information about his disappearance to call Crime Stoppers on 1800 333 000 or Launceston police on 131 444.