A river in Arunachal Pradesh suddenly turned black leading to death of thousands of fish, news agency PTI reported on Saturday. The officials have warned people against eating the fish found floating on the surface of Kameng river, the news agency further reported.

The district officials have pointed towards the high content of total dissolved substances (TDS) as the reason for the river, situated in East Kameng district, turning black.

PTI quoted district fisheries officials as saying that the TDS leads to breathing issues for aquatic species. The fish under the water are also experience reduced visibility due to high level of TDS, the officials further said.

The TDS in the Kameng river was 6,800 mg per liter, much higher than the normal range of 300-1,200 mg per liter, said District Fisheries Development Officer (DFDO) Hali Tajo.

Meanwhile, the residents of Seppa village, where the incident took place, have blamed China, claiming the TDS level went dangerously high due to the construction activities being carried out by the neighbouring country across the border.

Seppa East MLA Tapuk Taku appealed to the state government to immediately constitute a committee of experts to ascertain the cause behind the abrupt change in the colour of the Kameng river's water and the death of a large quantity of fish.

"If it continues for more than a few days, the aquatic life from the river will be totally eliminated," PTI quoted him as saying.

Earlier this week, India picked up increased activities and intensified patrolling by China's People's Liberation Army (PLA) in sensitive areas across the contested border in Arunachal Pradesh.

The data accessed by Hindustan Times showed that the Indian Army detected PLA's increased operational tempo in Lungro La, Zimithang and Bum La, which are areas of historical significance in the context of Chinese aggression in the eastern sector. The army further told HT that counter measures have been taken.

The army used satellites, long-range unmanned aerial vehicles, superior network of radars and hi-tech night vision systems to monito PLA's activities. The surveillance picked up increased vehicular movement due to infrastructure development activities and a large number of excavators and bulldozers to keep road axes open across the Lungro La, Zimithang and Bum La sectors, an official told Hindustan Times.

In 2017, a similar blackening of Siang river at Pasighat was reported. At that time, then Congress MP from Arunachal East Ninong Ering had written to Prime Minister Narendra Modi, seeking his intervention, claiming that it was the result of the construction of a 10,000-km-long tunnel in China, which diverted water from Siang to Xinjiang province in the Taklamakan desert.