Police don't think a letter from Tom Phillips is recent, or relevant to their search for him and his three children.

Their mother, Cat, posted the letter on social media, while begging the public to help.

Searches around Marokopa continue, with the $80,000 reward for information expiring in five days.

Newshub reporter Karen Rutherford is in Marokopa - and she says there are strong indicators an end to the search is near.

"They know who they're looking for and they know who they're targeting with this $80,000 reward. They are hoping that someone in that wider circle will cave."

LISTEN ABOVE