HONG KONG, May 2 (Xinhua) -- Hong Kong police seized a homemade bomb and some poisonous and inflammable chemicals at a wasted school in Kowloon Bay on Saturday, the 11th time for the police to find explosives in Hong Kong since social unrest last year.

Li Kwai-wah, senior superintendent of the Organized Crime and Triad Bureau, said the homemade bomb was discovered at a men's room of the school, along with remote control devices, a pressure cooker and four kgs of ammonium nitrate explosives after the police received a report at noon.

Li said finding the pressure cooker was an alarming signal as the seemingly harmless kitchenware is frequently used in terrorist attacks across the globe.

It is reported that an explosive device made of a pressure cooker containing bombs, nails and other hard objects will cause more casualties after being detonated remotely by a mobile phone or an alarm clock.

About 10 kgs of chemicals including quicksilver were also seized during the operation, which is suspected of being stolen from the laboratory of the Hong Kong Polytechnic University during the two-week occupation by rioters in November.

The police also said Saturday evening that a 15-year-old male and a 46-year-old female were arrested for throwing petrol bombs on the street and possessing gasoline with intent to damage property.