GAUCHAR, India — An air force helicopter returning from a rescue mission in flood-ravaged northern India hit a mountain and fell into a river, killing the eight people on board, officials said.

Bad weather has hampered rescue efforts in Uttarakhand state, where more than 1,000 people are believed to have died and thousands of others remain stranded in remote areas because of landslides and floods triggered by torrential monsoon rains. Other air force helicopters were unable to take off due to poor visibility, Group Capt. Sandeep Mehta said.

The air force has ordered an inquiry into the crash in the temple town of Kedarnath, said Priya Joshi, an air force spokeswoman. Five crew members and three civilians were on board the helicopter, she said.

Joshi said 45 aircraft were involved in rescue and relief operations in Uttarakhand.

Hundreds of thousands of Hindus make the Char Dham Yatra to four temple towns in Uttarakhand each year, usually returning home before monsoon rains in July make the mountainous area much more treacherous. Unprecedented heavy rains fell around mid-June this year and caught many unaware.

Air force chief N.A.K. Browne has assured flood survivors that the air force would rescue everyone stranded in Uttarakhand, but bad weather and poor visibility have frequently canceled the evacuation flights.

About 90,000 people from hundreds of villages and towns hit by the floods have been rescued. Landslides flattened entire towns, roads were washed away and communication links snapped, cutting off many people and necessitating air rescues.

Troops are also trying to rescue about 5,000 people who remain stranded in Badrinath town eight days after the torrential rains began.

In the town of Gauchar, the center of the rescue and relief operations, authorities made arrangements to send about a dozen Hindu priests to Kedarnath. The temple is one of Hinduism's most revered pilgrim sites.

Home Minister Sushilkumar Shinde had said deaths in Uttarakhand would exceed 1,000; at least 600 bodies were found buried in silt in and around the Kedarnath temple.

Authorities were preparing to cremate hundreds of flood victims' bodies. Truckloads of wooden logs were loaded onto air force transport planes and flown to Kedarnath to be used in a mass funeral and cremation. Medical teams are taking DNA samples and photographs of the unidentified bodies before they are cremated.

The federal health ministry said Tuesday it has sent more than 1 million chlorine tablets to purify drinking water supplies in Uttarakhand. The ministry has also sent several teams of doctors to help flood survivors.