A helicopter hit a wall and burst into flames as it was trying to land in India's remote northeast Tuesday, killing at least 17 people, police said. The MI-17 helicopter with 23 people on board was trying to land in the Buddhist pilgrimage town of Tawang near the border with China, said S.N. Mosobi, a police superintendent. Mosobi said the six who survived were in a hospital in Tawang, where the condition of at least three of them was described as critical. Seventeen people were killed. There were 18 passengers and five crew members aboard the Pavan Hans helicopter, which was on a regular flight between Tawang and Gauhati, the capital of Assam state. It was not immediately clear whether the crash was caused by bad weather or a technical problem, said Jambey Tsering, an official from Arunachal Pradesh state, where Tawang is located. Helicopters are commonly used in India's remote northeastern states, where dense forests and mountains coupled with poor roads that often become blocked during the monsoon season make land travel difficult.