Over 300 students in Guwahati formed a human chain on Monday to demand action to save the Brahmaputra river from contamination, The Times of India reported. The Assam government said on Saturday that the river’s water has become unsuitable for daily use after an “unusual phenomenon” of excessive turbidity and change in colour.

Members of the All Guwahati Students Union gathered to protest on Monday on the banks of the river near the Raj Bhavan.

“The Brahmaputra is the lifeline of Assam and it’s an extremely serious situation now,” the All Guwahati Students’ Union said in a statement, according to The Assam Tribune. “Unfortunately, the Centre has remained a mute observer to the disturbing developments.”

The student body said a polluted Brahmaputra would adversely impact agriculture, aquatic life, fishery and related livelihoods.

It also asked the government to hold talks with China immediately to resolve the matter, as Health Minister Himanta Biswa Sarma said on Friday that the construction of a dam or an accident in China had caused the contamination. China has denied the reports.

“Bharatiya Janata Party came to power in the state with a promise to protect jati, mati, bheti [community, land and homestead],” All Guwahati Students’ Union President Rajmil Ali said. “We are highly dissatisfied with the role of the ruling government as they haven’t shown any promptness in trying to unearth the causes behind this serious calamity.”

The Assam government has already sent samples for testing to the Indian Institute of Chemical Technology in Hyderabad and the Indian Institute of Technology in Guwahati.

The turbidity of water samples collected from Mainjanghat, Bogibeelghat and Jahajghat areas were 296 NTU, 404 NTU and 162 NTU, the government said. NTU, which means “Nephelometric Turbidity Unit”, measures the concentration of suspended particulates in a liquid. Permissible turbidity for potable water is 5.