Dozens of people have been detained at Kushtau Hill in Russia's Bashkortostan region following clashes between environmental activists and workers of the Bashkir Soda Company (BSK).
Police detained some 50 people on August 15 and transported them by bus to the city of Sterlitamak, some 20 kilometers to the east.
Defense lawyer Garifulla Yapparov told RFE/RL that police said they intended to hold the detainees for 48 hours.
The incident erupted after a coalition of unions representing chemical workers in Bashkortostan, including BSK employees, called a "flash mob" near an encampment set up earlier by environmentalists to block BSK’s exploitation of the hill, which is a protected natural resource.
BSK security contractors and OMON riot police clashed with the activists.
About 150 people remain at the encampment, and the BSK security personnel have reportedly left.
One activist told RFE/RL that some of the environmentalists were injured, but this information could not be confirmed. Activists said tear gas had been used against them.
In 2019, the company was granted a license to develop the hill for 20 years, despite a public outcry. BSK has said its work in the area will not harm the environment.
"This is not a protest or a march, but a flash mob, which does not require permission" from the authorities, organizer Guzel Miroshnichenko said.
"The goal of this activity is to support BSK workers who might lose their jobs if the factory is shut down because of a handful of hill-huggers, most of whom do not even live in Sterlitamak or the surrounding area."
He denounced the activists as "Wahhabis and nationalists who are members of banned organizations and supporters of the odious [liberal] politician [Aleksei] Navalny."
The pro-BSK flash mob came on the heels of a flash mob organized by the environmentalists on August 9 that attracted more than 3,000 people to the area, including human rights activists from the Human Rights Council of Bashkortostan's government and members of the group Bashqort, an ethnic Bashkir association that was banned as an "extremist group" in May.
That flash mob formed a "living chain" that stretched about four kilometers and included prominent regional academics, artists, filmmakers, and other intellectuals.
The environmental activists plan to hold an "ecological clean-up" of the area on August 16.