A deadly wall of muddy water that swept away an Indian Himalayan town this week was likely caused by a rapidly melting glacier exacerbated by the rising effects of climate change, experts said on Thursday.

Four people have been confirmed dead with scores of people still missing after water and debris tore down a narrow mountain valley, smashing into the town of Dharali in Uttarakhand state on Tuesday.

Several people could be seen in videos running before being engulfed as waves uprooted entire buildings, leaving others smothered in freezing sludge.

Government officials said shortly after the disaster that the flood was caused by an intense "cloudburst" of rain.

However, experts assessing the damage suggested that that was only the final trigger, adding to days of prolonged rains that had already soaked and loosened the ground.

PK Joshi, of New Delhi's Jawaharlal Nehru University, an expert on Himalayan hazards, said it appeared the flood was caused by the collapse of debris – known as moraine – that had dammed a lake of meltwater from a retreating glacier. He added that the persistent rainfall over the preceding days or collapse of a moraine-dammed lake contributed to the "sudden high energy flash flood".

Cloud cover has obstructed satellite imagery to check for the exact source of the debris, and Joshi cautioned that there was not enough satellite data for a "definitive confirmation".

Himalayan glaciers, which provide critical water to nearly two billion people, are melting faster than ever before due to climate change, exposing communities to unpredictable and costly disasters, scientists warn. (AFP)