Police in Hong Kong raided a homemade-explosives manufacturing lab ahead of another weekend of protests in the semi-autonomous Chinese territory.

Banners voicing opposition to an extradition bill that has sparked more than a month of demonstrations were found at the lab, according to Hong Kong media reports. Police said the investigation was continuing and that they had not found concrete evidence linking the explosives-making to a major protest march planned for Sunday.

Police said they found about 2 kilograms (4.4 pounds) of TATP, or tri-acetone tri-peroxide, in the late Friday night raid.

Alick McWhirter, a senior bomb disposal officer, said the homemade explosive is very unstable and extremely powerful. One kilogram was detonated Saturday morning. Public broadcaster RTHK said a 27-year-old man was arrested. Police said more arrests may follow.

Police have erected huge barricades near government headquarters in preparation for Sunday's march. Earlier protests have often ended with police clashing with groups of protesters who try to

occupy streets or refuse to disperse after the demonstration is over.

A counter-rally in support of the police was held Saturday evening. Thousands of people under umbrellas and overcast skies filled a park in central Hong Kong. A giant screen behind a stage for speakers read "Safeguard Hong Kong." Many wore white, heeding a call by organizers, and did not wear masks or helmets, RTHK said.

Many of the anti-extradition law activists wear black and don protective gear against police pepper spray and batons.