Hong Kong police said they had seized roughly 4,000 petrol bombs from the Polytechnic University campus which has been the battleground of recent protests.
Police seized petrol bombs, chemicals and offensive weapons, they said, adding that they removed dangerous materials and evidence on Thursday and Friday.
The campus has now been handed back to university management after being searched by police.
A police spokesperson criticised protesters for "taking hostage of the university and using it as a weapon factory".
The spokesman, speaking at a press conference on Friday (Nov 29) added that the case was "alarming" as "dangerous items and explosives [were] in the hands of young students".
The university was the scene of violent protests on November 17.
Protesters had used petrol bombs, bows and arrows and catapults against police, but police later laid siege to the university, trapping protesters inside.
Recent elections in Hong Kong resulted in a surge in pro-democracy candidates who secured almost 90% of district council seats.
Protests in Hong Kong started in June over proposed legislation that would have allowed Hong Kong to extradite citizens to mainland China.
The legislation was suspended but protesters are now asking for an investigation into police violence.