The Monday floods swept through the Gunung Leuser national park on Sumatra island just after midnight following torrential rains, officials and rescue workers said.
Homes and guest houses along the banks of the Bahorok River were wiped out.
Most of the bodies were found on the banks of the river which runs through the park, renowned for an orang-utan nursery and sightings of the Sumatran tiger and rhinoceros.
“We are still searching for more bodies and survivors,” Djonny Sitorus, a search and rescue team official, told Reuters news agency.
“We have found 67 bodies,” he said, adding that only three so far had been confirmed as foreigners.
Edi Sofya, North Sumatra provincial spokesman, said by telephone from Medan that five foreigners were among the dead.
The region is popular for wildlife watching as well as rafting, camping and trekking. The floods hit at about 01:00 (18:00 GMT) as most people slept.
“Many houses were swept away,” Sitorus said. “We can’t reach some of the areas because the bridges have been swept away.”
“I am on top of the valley now…there are 40 bodies here”
Jon Purba, eyewitness
Indonesia’s rainy season usually starts in November and lasts until April. Much of Sumatra and Java islands were hit by heavy rain overnight.
Sofyan Tan, a manager of a guest house in the area, said up to 70 people had been killed. “The water is now about 10 metres deep,” Tan said.
Jon Purba, another hotel manager speaking from the Bukit Lawang valley, said: “I am on top of the valley now…there are 40 bodies here.”
A park official said the floods had not hit the primate conservation centre.