Dozens of bottles containing dangerous chemicals, including highly corrosive acids, were discovered on Thursday at a park here, prompting Hong Kong police to investigate if the substances had been stored there by anti-government protesters.

Emergency personnel were called in when the bottles, which contained chemicals such as sulphuric and nitric acid, were found at the Shing Mun Country Park, reports the South China Morning Post newspaper.

"Initial investigation showed about 50 bottles were seized... and some of the bottles contained sulphuric acid," a police source said.

The source said the case was being investigated by the crime unit from the police headquarters, a department that has been handling protest-related crimes during the social unrest that has roiled the city since June.

Personnel from the police tactical unit were also deployed to scout the area and firefighters were on standby at the site.

On Wednesday night, the police seized about 10,000 petrol bombs from Chinese University, Polytechnic University (PolyU), and other colleges and their surroundings, along with a large number of chemicals, offensive weapons and raw materials for explosives.

After a 13-day siege of PolyU occupied by more than 1,000 protesters, police on November 29 seized 4,296 petrol bombs, 671 bottles of chemicals and 622 pieces of weapons.

Some 810 people were arrested when leaving PolyU during the siege, while police took the details on a further 318 youngsters under the age of 18.