Flash floods triggered by heavy rains in two mountainous north Indian states have killed one person and left 26 others, mostly power plant workers, missing, officials said Saturday.

Nineteen workers were reported missing from a hydroelectric power plant after water gushed into the facility in Uttarakhand state's Uttarkashi region, local administrator R. Rajesh Kumar told AFP.

The workers were missing "following a cloudburst that hit the region" on Saturday, Kumar said by telephone from Uttarkashi, some 350 kilometres (220 miles) from the state capital Dehradun.

They were believed to have been working at a site on the plant that was under construction, officials said.

The plant belongs to state-run utility Uttarakhand Jal Vidyut Nigam Ltd., officials said.

"We have sent rescue teams to the project site as well to other areas hit by flash floods," Kumar said.

Seven villagers were also swept away in floods that hit the district of Uttarkashi, a Hindu pilgrimage site, Kumar said, while some devotees were stranded.

Authorities cancelled leave for essential workers and shut down several hydroelectric power projects in the state to guard against damage from the rains, Uttarakhand Chief Minister Vijay Bahuguna said in Dehradun.

Engineers were working on reopening blocked roads leading to popular shrines to enable the stranded pilgrims to leave the area, Bahuguna said.

Disaster management officials said scores of houses in the flooded area were damaged by the rains.

Torrential rains on Friday night also hit the nearby state of Himachal Pradesh, drowning a man in his vehicle, washing away several bridges and partly destroying a key highway, officials said in local capital Shimla.

India's monsoon rains that normally come each summer arrived late this year, meaning there has been little rainfall in almost half of the country, sparking fears of a drought.

Nevertheless, there has been heavy rainfall in places, with rains last month in the northeast killing more than 120 people and forcing another six million to flee their homes.