Hong Kong police arrested six more men on Wednesday in connection with the discovery of a homemade pipe bomb at a residential unit.

The move came a day after the arrest of four men, aged 21 to 29, in an operation where police defused a homemade bomb made using a metal pipe and found equipment suspected of being used to make explosives in buildings in Mong Kok and Sheung Shui.

Chin Chiu Suryanto and Chan Tin-chu. Photo: RTHK screenshot.

On Wednesday, six more men aged 17 to 23 were arrested – including two students and a kindergarten teacher – on suspicion of unlawful assembly, conspiracy to manufacture explosives and possession of drugs.

New Territories North Regional Crime Headquarters Senior Superintendent Chan Tin-chu said on Wednesday that police believed the ten arrested were from a “relatively hidden valiant group.” The term “valiant” has often been used to describe frontline guerilla protesters.

Some members of the group were on the run and being sought by the police, he added.

The homemade bomb. Photo: RTHK screenshot.

A family member of one of the people arrested at a village house in Sheung Shui said the sulphur found by police had been used to deter snakes, according to RTHK.

Asked how the police could tell common household items were used for unlawful means, Chan said that the goods could have been used to make something else despite being lawful. He said police will investigate whether the chemicals and equipment found could have been used to make explosives.

A small explosion occurred when police defused the homemade bomb at the Mong Kok unit on Tuesday, blowing a hole in the door of an elevator.

Photo: RTHK screenshot.

Chin Chiu Suryanto, a bomb disposal officer at the Explosive Ordnance Disposal Bureau, said the discovery of a homemade pipe bomb was a first in Hong Kong. Such explosives were more common overseas, he said.

“It would have generated a large amount of heat or even a fireball,” he added.

Asked why the police chose to defuse the bomb inside the building, Chin said that moving it would only increase its risk to other members of the public.