Hundreds of demonstrators in the eastern Chinese province of Zhejiang on Sunday were camped outside a solar-panel manufacturing plant accused of contaminating a nearby river.

BEIJING — In a fresh indication of growing public anger over pollution, hundreds of demonstrators in the eastern Chinese province of Zhejiang on Sunday were camped outside a solar-panel manufacturing plant accused of contaminating a nearby river.

The demonstration was the latest move in a four-day protest that has sometimes turned violent.

The unrest began Thursday, when about 500 residents gathered outside the plant, in Haining, roughly 80 miles southwest of Shanghai. Some protesters stormed the 5-year-old factory compound, overturning eight company vehicles, smashing windows and destroying offices. The next day, four police cars were damaged.

The factory is owned by JinkoSolar Holding, a Chinese firm with more than 10,000 employees that is listed on the New York Stock Exchange and reported total revenue in the second quarter of 2.3 billion renminbi, or about $360 million.

Some investment analysts described the company last year as a promising upstart in the solar-energy products business.

“Return our lives to us, stay away from Jinko,” read one protest banner that was photographed by a news agency. Company officials could not be reached for comment.

According to Chinese news reports, residents claimed runoff from solid waste laced with fluoride and improperly stored at the plant had been swept into the nearby river after heavy rainfall Aug. 26. They said a sea of dead fish rose to the surface, covering hundreds of square yards of water. Pigs whose sties had been washed with river water also were reported to have died.

The state-run China News Agency reported that government inspectors later found the water contained 10 times the acceptable amount of fluoride.

The Haining demonstrations follow a mass demonstration last month in Dalian, in northeast China, in which 12,000 people protested a new chemical plant that produces paraxylene, a toxic chemical used to make polyester products. Government officials promised to relocate the plant after the protest, one of China’s largest in nearly three years.

Ma Jun, the director of the nonprofit Institute of Public and Environmental Affairs in Beijing, said last month that protests over pollution are on the rise.

“People have a growing awareness of the damage caused by environmental pollution and a growing sense of rights,” he said. “There are an increasing number of cases that can be characterized as ‘not in my backyard.'”

According to Chinese news reports, the Zhejiang solar-panel plant had been faulted for improper waste disposal in April, and the government had ordered the company to suspend production until it constructed a facility to store solid waste safely.

The factory sits more than 100 yards from an elementary school and about 300 yards from a kindergarten, reported National Business Daily, a newspaper based in Beijing. A few protesters were reported to have been arrested on charges of theft or vandalism.

In one sign of the government’s growing concern over the potential of Twitter-like microblogs in China to stir unrest, a 33-year-old resident was arrested on charges of posting false rumors that 31 people had developed cancer and that six were stricken with leukemia in the nearby village of Hongxiao, which is close to the plant and has a population of 3,300.