Hundreds of people demonstrated on Thursday in eastern China over a new case of suspected lead poisoning of children, state media reported.
The protest, in front of the local government offices in Shanghang county of Fujian province, came after at least four children were found to have excessive levels of lead in their blood, Xinhua news agency said.
Parents blamed pollution from a local battery factory.
The protesters, who had failed to reach an agreement with the local authorities, blocked a highway for several hours, Xinhua said.
The protest follows two similar incidents in August -- in northern Shaanxi and in central Hunan province -- which saw a total of more than 2,100 children test positive for high lead levels.
Pollution-related health scares are common in China, where an emphasis on economic growth over the past three decades has lead to widespread disregard for environmental protection.