Police raided an armor factory suspected of manufacturing "flying bombs" that can be dropped on targets by drones following investigations into the bomb attack in Mong Kok on Sunday.
Three drones and three throwers that could be installed on drones were found along with a large amount of armor in a flat in Tai Kok Tsui after police intercepted two men on Larch Street at around 7.30pm on Tuesday.
The two, a 17-year-old student surnamed Ting and a 23-year-old man surnamed Tung, have been detained in relation to the bomb attack in Mong Kok that targeted police officers.
Two modified mobile phones - similar to the one that exploded in Mong Kong on Sunday - that can be used to detonate explosives were also seized.
Narcotics Bureau officers also seized six suspected petrol bombs and raw materials for making bombs, which were taken by officers from the Explosive Ordnance Disposal Bureau for examination.
Police also searched Tung's home, where they found three long knives, four short knives, 15 folding knives, a slingshot, four signal bombs and five smoke bombs.
Superintendent Raymond Chou of Narcotics Bureau said police will look into whether others are involved.
In a separate case, police arrested a 37-year-old construction worker suspected of inciting others to besiege government buildings and take part in illegal assembly through social media yesterday morning.
The man, surnamed Poon, was arrested at his home at about 7am.
Chief inspector Lau Wan-tat of Organized Crime and Triad Bureau said Poon posted false allegations on social media targeting police, such as rumors that some arrested people were beaten to death in detention. A computer and three mobile phones believed to be linked with the case were seized.
Lau said the operation is ongoing and did not exclude the possibility of further arrests.
"Most of the ordinances targeting crime prevention in the real world also apply in the world of the Internet, so please do not take the chance of committing crimes on the Internet thinking you won't be caught," he said.
Meanwhile, police are considering purchasing neck protectors for frontline officers, according to sources, after a secondary six student allegedly used a box cutter to slash the neck of a police sergeant on Sunday.