Hong Kong police said on Thursday officers would end the 12-day siege of the campus of Hong Kong Polytechnic University in Hong Hum as early as Friday (today) — but they did not provide a specific time frame.

The announcement comes after some 400 police and fire service officers finished a one-day operation to remove dangerous items and offensive weapons left by radical students and rioters who had barricaded themselves up on the campus.

Police seized more than 3,800 gasoline bombs, 900 gas canisters and 558 bottles of chemicals believed to be used for making explosives, noted Li Kwai-wah, senior superintendent of Organized Crime and Triad Bureau.

"Fortunately, we did not find any final products," Li told a news briefing on Thursday night.

Offensive weapons including 27 bows, 200 arrows and an air rifle found at the scene, he added.

Assistant Commissioner of Police (Operations) Chow Yat-ming said buildings and facilities on the campus were extensively damaged; some hazardous chemicals were found exposed under sunlight for a long time, posing a serious threat to the safety of people nearby.

Chow said police did not come across any protesters on campus during the latest operation. He refused to comment on whether there were still protesters inside the university.

Chow said their work is expected to be completed by Friday morning and a safe campus would be returned to university authorities.

PolyU issued a statement on Thursday evening, saying: "It is expected that the cordon around the campus can be removed tomorrow."

Conditions on the campus were more complex than expected, with facilities badly vandalized and dangerous materials widely scattered about, the statement read.

The university authorities conducted two searches of the campus on Tuesday and Wednesday respectively, but only found one remaining person.

Radicals fortified themselves in the campus on Nov 13 after clashing with police. So far, some 1,100 protesters have left. Most of them were arrested as they left; those needing medical attention were hospitalized.