Kierwiński said the situation in schools was stabilising, both in terms of public emotions and online activity.
He added that police would "maintain the forces and resources needed to ensure safety."
During the police operation, officers detained 192 people, and criminal proceedings were initiated against 106.
Police chief Marek Boroń said the proceedings mainly concerned criminal threats, public incitement to commit offences, false alarms, reports of threats and endangering others.
Since the operation began, police have secured 155 dangerous items. They have submitted 68 sets of materials to family courts and recorded 56 cases in which preventive or care measures were applied.
Police are also monitoring the internet.
Bartosz Furgała, deputy head of the Central Bureau for Combating Cybercrime, said 350 cybercrime officers were analysing online information to identify behaviour that could indicate a suspected crime or a threat to the lives and health of minors or the school community.
Furgała said officers had identified around 300 such cases. The bureau is working with internet and telecommunications operators, digital service providers and international partners, including Europol.
Police have examined half of the 160 pieces of seized equipment, Furgała said.
Kierwiński said that after a week of intensive work, there was no evidence that the recent incidents were linked. He said there was no confirmation of a nationwide online challenge, particularly one inspired by specific external groups.
The education ministry is preparing regulatory changes
Deputy Education Minister Paulina Piechna-Więckiewicz said a draft regulation on occupational health and safety would go out for consultation on Friday.
The draft would require school heads, working with the relevant services, to conduct practical exercises for different emergency situations at least twice a year.
Proposed measures include expanded powers for school heads to check personal belongings and secure dangerous items, clearer rules for responding to threats and cooperation, and stronger legal protection for teachers.
The new legislation is also intended to expand access to psychological and legal assistance for teachers.
The measures follow several violent incidents involving sharp objects at schools in the Mazowieckie region last week. One incident resulted in the death of a 37-year-old school employee.
(sp)
Source: PAP