New Delhi, India (CNN) -- India's air force unsuccessfully struggled to trace a helicopter carrying the top leader of a state bordering Tibet a day after it disappeared in the remote mountainous region, officials said Sunday.
The helicopter, belonging to the government-run Pawan Hans company, took off from Tawang for Itanagar in Arunachal Pradesh state Saturday at 9.45 a.m. Authorities sounded an alert for it when it did not arrive for landing.
The helicopter, carrying Arunachal Pradesh chief minister Dorjee Khandu and four others, remains missing, said Avinash Kumar Mishra, the state's resident commissioner in New Delhi, Sunday.
He told CNN the search would resume Monday morning.
According to Mishra, the helicopter did not go outside Indian airspace into neighboring Bhutan, as some initial reports, rejected by officials later, suggested. "That's completely ruled out. It is missing within the Indian territory," Mishra said.
On April 20, at least 17 people were killed as a Pawan Hans helicopter crashed in Tawang upon landing and caught fire, officials said.
Arunachal Pradesh has been the center of a tense struggle between India and China.
The two giant neighbors fought a brief but bitter border war in 1962 over the hill territory.
India insists Arunachal Pradesh is its "integral" and "inalienable" part. China lays claim to 90,000 square kilometers (34,750 square miles) of land in that Himalayan region governed by India.