Hong Kong police and firefighters have entered the Hong Kong Polytechnic University on November 28 to search for dangerous chemicals. Photo: Yin Hao/GT

Hong Kong police on Friday said they had seized nearly 4,000 petrol bombs, 1,400 pieces of explosives materials, 600 items containing corrosive liquids and 570 weapons during the two-day evidence-collection procedure at the Hong Kong Polytechnic University, which was reopened at about Friday noon after being occupied by rioters for 13 days. 

As of November 29, 5,890 people have been arrested by the police in the months-long unrest in Hong Kong for illegal gatherings and riots, including 1,377 related to violent actions at the Polytechnic University, Hong Kong police announced. During the same period, 483 Hong Kong police officers have been injured when dealing with riots.

Police did not find any remaining individuals on campus during the two days, according to Hong Kong media. 

Some suspicious materials including washing-up liquid were also found, and police said they had not yet determined whether they were used to make dangerous goods.

The university's vice president told media that it would take some time to clear and rebuild the campus, which has been destroyed by the rioters. 

According to local media, the glass windows and doors on the campus have all been smashed, and laboratories have been vandalized with paint on the walls and chemical containers scattered on the floor. A Starbucks shop on the campus was also destroyed. 

Hong Kong police on Friday morning completed their collection of evidence, seizing 280 petrol bombs, 318 cans of cassette gas, 28 buckets of chemicals and other offensive weapons from the campus.

Police said they would lift the blockade around the campus after the removal of dangerous goods, according to local media. 

Police also found large number of glass bottles that could be used to make Molotov cocktails.

The campus was blocked on November 17 following clashes between the police and some rioters, after which more than 1,000 rioters remained inside, destroying campus facilities and confronting the police. 

Police, firefighters and members of the explosive ordnance disposal bureau entered the Hong Kong Polytechnic University on Thursday after the majority of the rioters had surrendered.