Rescuers found five bodies Monday and were searching for 20 more people feared dead in northern India after they were swept away by a sudden surge of water released from a dam, officials said.

Rescue workers were scouring the Beas river for 19 students and a guide who were missing after being hit by the wall of water on Sunday night in the Himalayan state of Himachal Pradesh.

The engineering students, who were on a college trip, were standing on the banks of the river taking photographs when the water came racing downstream from a hydroelectric power plant.

"So far five dead bodies have been retrieved," the National Disaster Response Force said in a statement.

Fifty students had been travelling on buses to the tourist hill station of Manali when they stopped in the Kullu Valley, some 200 kilometres (130 miles) from the state capital of Shimla, officials said.

As the search continued, anger mounted among students and teachers who said they received little warning before the water hit.

"I tried to alert my friends... I ran towards my friends but by then, the water level had shot up," student Ravi Kumar told the Press Trust of India news agency.

"I tried rescuing four or five of them but in a matter of seconds, the water had risen to five to six feet," he said.

"My friends lost their footing and drowned before my eyes," he said.

Some 84 soldiers, divers and other rescue workers were searching for the students as their distraught parents arrived from the southern city of Hyderabad where they all live.

Rescuers were seen combing the banks of the river, while others in kayaks and inflatable dinghies were checking the water downstream. Television footage showed soldiers carrying a body bag from the river to a waiting jeep.

"It is very difficult to retrieve the bodies due to deep cavities at the dam site," senior police officer Rakesh Kanwar told reporters.

- Inquiry ordered -

Himachal Pradesh Chief Minister Virbhadra Singh ordered an inquiry into the cause of the accident, while local media reported that several engineers from the state-run Larji power project have been suspended.

"If any negligence is found on anybody's part, suitable action will be taken," Singh told reporters from the site where a string of top politicians gathered throughout the day.

India President Pranab Mukherjee expressed his sadness at the tragedy and urged authorities to prevent a similar incident from happening again.

"Necessary action may please be also taken to investigate the cause of the accident and ensure that such mistakes do not happen in future," the president said in a statement.

Mandeep Singh, an engineer from the hydroelectric plant, said a "warning hooter" was sounded before the water was released but "the warning was not heeded."

An unnamed student told reporters that "many of us did not understand the warning sound and by the time we did it was too late."

Himachal Pradesh and other Himalayan states, including neighbouring Uttarakhand, are home to a string of hydroelectric projects as India rushes to expand power generation to meet rising demand.