"Rescuers have found some of the missing people on higher ground in North Pagai island," disaster management official Agus Prayitno told AFP, adding that 163 people were now listed as missing compared to 298 earlier today.
He said the official death count had not changed from the 413 provided earlier.
A three-metre (10-foot) tsunami triggered by a powerful 7.7-magnitude earthquake slammed into North and South Pagai islands late Monday night. The islands are in the remote Mentawai chain off western Sumatra.
Joskamatir, a disaster management official on North Pagai island, said the missing people had been too scared of another tsunami, to leave the forests and hills above their shattered homes.
"It took days to find them because they didn't want to return to their villages as they were afraid that a tsunami would hit again," he said.
"We're so grateful that we've found many of the missing people -- we'd been working very hard to find them," he added.
Officials had held little hope of finding many of the missing after flights over the area earlier in the week had revealed dozens of unclaimed bodies strewn across beaches and wedged in rubble.
Many of the dead were also believed to have been sucked out to sea as the killer wave receded.
An AFP photographer on North Pagai said survivors were still wandering between villages looking for their missing loved ones today, as rescue workers struggled to reach the isolated communities.