The two-tonne copper Pillar of Shame was first exhibited at a Tiananmen Square commemoration in Hong Kong in 1997, the same year Britain handed the city back to China.
Government said a warrant was obtained to look for evidence of suspected violation of the national security law
Some 40 grams of low explosives were inside the bomb, but it remains unclear what the substance was.
The Polytechnic University said that it has decided to halt its search after a sweep of the trash-littered campus for a second straight day failed to find anyone left behind.
