HONG KONG - Police arrested two women on Thursday in connection with a package of powerful explosives in Sheung Shui that authorities believe was meant for large-scale public activities.

The women, who are suspected of manufacturing explosives, are the wife and the mother of a man arrested two days ago during a police’s raid operation in a Sheung Shui residential unit that police said was a laboratory for making dangerous chemicals. The explosives seized on Thursday were believed to be made in that unit.

Police said the package was buried in farmland in front of the residential unit. Preliminary tests showed that the 100 grams of yellow powder in the package were high explosives. The power and effectiveness of the explosives still have to be assessed, police said.

Police said bombs that use such explosives can cause multiple casualties, adding that these explosives were made to attack police officers or vandalize police facilities at mass public events.

On Monday, police defused a homemade pipe bomb in a subdivided apartment in Mong Kok. Ten people have been arrested on suspicion of being connected to the Mong Kok bomb.

Making explosives with the intent to endanger life or property is a serious crime punishable by up to 20 years’ imprisonment.

On Wednesday, the city’s security chief John Lee Ka-chiu warned of the high risk of homemade bombs, adding that the bureau will beef up precautions against homegrown terrorism.