Helicopters of the Indian Air Force evacuated 30 people stranded on an island in the swelling Siang river in Arunachal Pradesh on Friday, Chief Minister Pema Khandu said.

“The rescue mission started at 4.30 am and was over in an hour,” said Deputy Commissioner of East Siang district Tamiyo Tatak. “Four youths and an elderly man chose to stay behind,” Hindustan Times quoted him as saying.

Tatak said the people were trapped on the island in Sille-Oyan circle as rescue boats could not be sent due to the rising water level and unusually high waves in the Siang river. Tatak also said the water level in the river has increased a bit since Thursday, but there was no cause for panic. “We are monitoring the situation constantly.”

The East Siang district administration issued a circular on Wednesday asking people living on both sides of the Siang river to remain alert “but not to panic”. The circular states that as per reports sent to New Delhi by Beijing “due to heavy rainfall in Chinese portion, the Tsangpo river is swelling with observed discharge of 9,020 cumecs” at 8 am on Wednesday.

Meanwhile, large scale soil erosion has been reported in areas of Pasighat in East Siang district due to the rising water levels and high tides in Siang river, reported Northeast Today on Thursday. At least eight houses in Seram village have already been eroded.

Last week, East Siang district officials had asked people not to enter the water as the flow of the river was fluctuating over the past two weeks “with unusual waves”.

In Assam, Dibrugarh district is on alert due to a “gradual rise in the water level of the Brahmaputra”. “But it is not flowing over the danger mark in Dibrugarh,” Dibrugarh Deputy Commissioner Laya Madduri said on Thursday. “There is no cause to panic yet.”