Hong Kong police said on 15 June that they had arrested nine people after finding what are believed to be explosives in a vacant suburban studio.
The suspected explosives were found in the Sai Kung area of the city's New Territories, at the beginning of a week of protests outside the city's government buildings to protest proposed changes to the semi-autonomous region's electoral system.
"Nine people have been arrested in relation to the discovery of suspected explosives," a police spokesman told the New York Times.
The people arrested have not yet been named by authorities, but among them are a student and teaching assistant, reported Reuters. The South China Morning Post says that five of the suspects are male and four are female.
A police superintendent confirmed that officers had found "several kilograms of solid substances and five litres of liquid substances we believe to be chemicals linked to [the making of] explosives".
At another location police found the raw materials of the the explosive triacetone triperoxide(TATP), used in the 7/7 bombings in London and attacks in Israel, as well as air guns and maps showing potential targets, including government buildings.
RTHK, citing police sources, reported that some of the suspects arrested belonged to a radical protest group that rejects mainland Chinese control of the city and calls for open and free elections.
A new bill is to be presented to the city's legislature on 15 June, which will compel election candidates to be approved by a panel of officials loyal to Beijing.
Protesters have vowed to block the legislation. Police have put up metal fences around the local government building and warned protesters not to take "any violent or aggressive action".