The incident last week is being attributed to a former employee of the Interior Ministry’s IT development department, which runs computer systems for all Estonian internal security agencies, writes Eesti Päevaleht newspaper today.

According to the authorities, access to the actual content of the mailboxes was not gained. Nevertheless, Estonian Interior Minister Mr Hanno Pevkur, Chief of Police, Mr Elmar Vaher, and more than ten other officials found their mailboxes blocked last week.

It is thought that the mailboxes were blocked by simply running wrong passwords until IT systems locked the accounts as a precaution.

"A criminal investigation has begun, therefore we cannot comment on the incident," said prosecutor Piret Paukštis.

Eesti Päevaleht adds that this week Mr Pevkur received an anonymous letter from a former specialist at the IT development department, which accuses the unit of abusing spyware to keep tabs on its own employees. The letter claims that the Estonian ministry is using to this end the controversial FinSpy software.

Apparently another former employee said already in April that the ministry’s IT arm has set up a system that is "in principle, equal to the PRISM system allowing to gather compromising material on its employees".