He pointed out that 37 of the arrestees were aged below 21, and 16 of them were students.
The figure was recorded between February 14 – when etomidate, the drug’s main ingredient was classified as a dangerous drug – and Thursday.
Siu told reporters that police have stepped up enforcement.
“Apart from stepping up street patrols, we also have a lot of intelligence-led operations,” he said.
“Among the 120 cases, the arrests for 70 of the cases were carried out on the streets, and another 50 were made in non-public places.”
He emphasised that all stakeholders, including school principals and teachers, as well as social workers, play a crucial role in tackling the space oil drug issue.