Protests have resumed in an eastern Chinese city where thousands of residents clashed with police while demonstrating over the proposed expansion of a petrochemical factory.

Several hundred citizens of Ningbo city in Zhejiang province set off from a city square and headed for the offices of the city government on Sunday morning. Children were among those who marched and parents carried babies in their arms.

On Saturday, residents reported that protests had turned violent after authorities used tear gas and arrested participants. Authorities said “a few” people disrupted public order.

On Sunday, several dozen uniformed police officers stood around and some walked with protesters, appearing to allow them to express their grievances without taking action.

Some protesters wore face masks and shouted slogans including “Protect Ningbo” and “Return my health.”