Officials in Uttarakhand state said about 90 rest houses for pilgrims had been washed away by high water in the Himalayas, possibly causing many more than the 150 deaths officially acknowledged, The Times of India reported Thursday.
More than 15,000 people on a pilgrimage to a Sikh place of worship have been evacuated to relief camps, a police official said.
About two dozen helicopters and a military mountain rescue team have been called in to rescue hundreds of stranded tourists.
Aid efforts were operating on a war footing, officials said. Scores of villages remain underwater as waters from at least six rivers continue to rise.
Unusually early and heavy rains caused the flooding that Vijay Bahuguna, Uttarakhand's chief minister, called a "Himalayan monsoon," CNN reported.
The vice chairman of the National Disaster Management Authority said the rains in the state were "the heaviest in 60 years," the BBC reported.
Some of the worst devastation has been in the ancient holy city of Kedarnath where shrines are now filled with mud and rocks.
While meteorologists say conditions have improved somewhat, the floodwaters have reached the Indian capital of New Delhi where the Yamana River has overflowed into shops and homes.
Some 5,000 people in the capital have been relocated, authorities said.
The Indian states of Himachal Pradesh and Uttar Pradesh, as well the neighboring country of Nepal, have also reported flood-related deaths.