The Sutlej river flooding has caused damage estimated at $183.7m

Officials say they are not sure when they can run the mammoth 1,500 MW Nathpa hydro project, located in the northern state of Himachal Pradesh.

Thousands of people were left stranded after the level of the Sutlej river rose in Himachal Pradesh on Sunday.

They include several hundred tourists who are being rescued by helicopter.

Twenty-nine foreigners are among those who have been evacuated.

Tibet flood

Although the level of water has receded, officials say they are still on a flood alert.

"It is the high silt content which is forcing us to keep the [Nathpa] project closed," a top official at the power project told the BBC.

"On Tuesday, the silt content was more than 15 times higher than the permissible limit," he said.

The Nathpa project houses Asia's largest underground power complex and only came into operation last May.

It supplies states across northern India as well as the capital, Delhi.

It is not yet clear what caused the water level to rise but officials said it could be due to flooding in Parechu lake in neighbouring Tibet, which has affected the Sutlej further downstream.

The overflowing river destroyed villages, farmland and roads with the damage estimated at eight billion rupees ($183.7m).

In 2000 floods on the Sutlej killed about 150 people in Himachal Pradesh.