RTHK has learnt that the sister-in-law of national security suspect, Nathan Law, was taken away by security police on Saturday.

Officers are understood to be looking into whether she helped him endanger national security from overseas.

The suspect's parents and brother were also said to have been questioned last month.

Police have offered a reward of HK$1 million for information that leads to the arrest of Law, as well as seven other suspects who are currently overseas.