Bomb experts were called in after police arrested a man and seized a package of suspected explosive substances at a private housing estate in northern Hong Kong on Monday. A source in the force said initial examination showed the package contained suspected explosive precursors such as potassium nitrate, along with firecrackers and gas masks. An explosive precursor is a chemical substance used in the manufacture of explosives. Detectives from the force’s organised crime and triad bureau (OCTB) apprehended the man outside Block 6 of Wing Fok Centre on Luen Chit Street in Sheung Shui soon after 2pm. Explosives found at train station on Hong Kong’s border with mainland China “A 50cm-long package containing suspected explosive substances was found during the operation,” another source said. The section of Luen Chit Street was cordoned off and officers from the explosive ordnance disposal bureau were called in. As of 5pm, the experts were still investigating the package and the OCTB operation was under way. A police spokeswoman said no evacuation was needed. The second source said the arrest could be linked to anti-government protests . Hong Kong had been gripped by months of social unrest from June 2019, with major protests sparked by the now-withdrawn bill that would have allowed the transfer of suspects to jurisdictions, including mainland China. 14kg of dangerous substances and improvised bomb found at abandoned school site With signs of the protests waning in 2020 amid the Covid-19 pandemic and with the national security law in force, police have resumed regular work. Beat policemen have also returned to the streets. Foot patrols were halted in August last year, amid a staff crunch and the risk of officers being attacked by protesters. As of the end of December last year, police had arrested 10,200 people in connection with the unrest and 40 per cent of them were students. Among them, 2,450 were prosecuted. Since June 2020, 97 people have been arrested under the national security legislation, which outlaws acts of subversion, secession, terrorism and collusion with foreign forces. Offenders face life in prison.