Twenty-one people who police say violated the law during a protest on Sunday against the planned construction of a garbage incineration plant in Zhaoqing, Guangdong province, have been taken away for questioning.

"The lawbreakers threw stones and bottles of mineral water at police and other law enforcement personnel during the protest in Lubu township in Zhaoqing's Gaoyao district," said Duan Jianxin, an official in the city's publicity department. "Some police officers were injured."

Police urged those who violated the law during the protest to give themselves up, he said.

Duan, who was at the scene to help maintain order, declined to provide details about the protest, citing the ongoing investigation.

"After being educated and persuaded, the villagers have dispersed, and the situation has been resolved," Duan told China Daily on Sunday.

According to a statement from the Gaoyao district government, several hundred people gathered in front the Lubu government building to protest construction of the incinerator at 9 am on Sunday.

More than 1,300 protesters and onlookers were recorded during the peak hours. The gathering caused a heavy traffic jam in the area, the police said. They encouraged residents to abide by the law when expressing themselves to government departments, and to avoid believing and spreading rumors.

Order was restored by about 2:30 pm.

Some villagers said they were worried the project would create air and water pollution after it begins operation.

Sources in the Zhaoqing bureau of environmental protection said the incineration plant is a key environmentally friendly project for the city, located in western Guangdong.

The incinerator is designed to burn 365,000 metric tons of garbage annually, while generating more than 94 million kilowatt-hours of electricity. It would handle 1,500 tons of garbage a day and serve more than 1.6 million residents from Zhaoqing's Duanzhou, Dinghu and Gaoyao districts, as well as some people in Deqing county, which is under the administration of Zhaoqing.

The project meets the State's environmental requirements, sources said.