All 20 people on board a helicopter that crashed on Tuesday while on a rescue mission in Uttarakhand have died, said Air Chief Marshal NAK Browne.

Five of those killed were from the air force; the others belonged to the National Disaster Response Force and the Indo-Tibetan Border Police. 12 bodies have been found so far. Commandos are searching the narrow valley where the helicopter crashed.

The air chief said the cockpit voice recorder and flight data recorder of the crashed helicopter have been recovered. It's not clear yet if the crash was caused by bad weather or technical problems, he said.

Meanwhile the State Government today declared a day's mourning as a mark of respect to those killed in the crash.

Chief Minister Vijay Bahuguna visited Jolly Grant helipad of Air Force this morning and offered his condolences to the soldiers. He said if children of the killed soldiers take education from the State, the Government will bear their education cost.

An Air Force spokesperson told our correspondent that a court of inquiry into the incident has been ordered. It will be conducted by a Wing Commander or Group Captain level officer from the force.