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Jessica O'Connor and Dion Reynolds, both 23 and from the Tasman area, entered the park on 9 May.
Police say no heat or light sources were spotted by the Royal New Zealand Air Force NH90 helicopter that searched inland from the Anatori River mouth overnight.
The police said the air and ground searchers have commented on the density of the bush which makes searching difficult.
Three teams who were searching overnight have now been replaced, and those three teams will today do detailed searches of the hills.
A search dog that was assisting in the search last night has also been swapped out due to continuously working on the rough terrain.
Late last night two other teams were winched into the river's headwaters and today will work their way downstream.
The police say the number of searchers is expected to grow throughout the day.
They are also continuing to make use of the USAR drone that will search the wider area for heat and light.
The police said search management have been making extensive enquires to try and corroborate differing reports of the trampers expected return date.
They are also yet to confirm if either the footprints or a historic campsite located near the Webb River yesterday belong to the two trampers.
Police are asking for anyone who has been around the Anatori, Webb, Kokopu, Independent and Fraser rivers since 8 May and who may have seen the pair to get in touch.
Anyone with information should contact Police on 105 and quote event number P042228949.