Two men have been arrested after hackers stole the data of 8,000 children from a London nursery chain database.
Met Police officers confirmed they had taken a 17-year-old and 22-year-old into custody where they remain for questioning.
An operation was conducted at a number of residential properties in Bishop's Stortford, Hertfordshire, where the duo were detained on suspicion of computer misuse as well as blackmail.
It follows the pictures, names and addresses of around 8,000 children being stolen from the Kido nursery chain.
Cyber criminals said at the time they were using the details to demand a ransom for the company, which has 19 UK sites - 18 in Greater London and another in Windsor.
Kido also operates 39 nurseries across India and others in China as well as nine sites in the US - six in Houston, two in Austin and one in Chicago.
Will Lyne, Met's Head of Economic and Cybercrime, said: 'Since these attacks took place, specialist Met investigators have been working at pace to identify those responsible.
'We understand reports of this nature can cause considerable concern, especially to those parents and carers who may be worried about the impact of such an incident on them and their families.
Details relating to around 8,000 children were stolen from a nursery chain (stock image)
'We want to reassure the community and anyone affected that this matter continues to be taken extremely seriously.
'These arrests are a significant step forward in our investigation, but our work continues alongside our partners to ensure those responsible are brought to justice.'
The hackers previously claimed to have safeguarding notes and details about the children's parents and carers.
They had allegedly contacted some parents by phone to try and extort money from the nursery chain, which runs services for children as young as six months old.
The hackers told the BBC they 'weren't asking for an enormous amount' although it was 'of course' about money - and 'deserve some compensation for our pentest'.
A 'pentest' refers to a so-called penetration test, when ethical hackers are hired to check the security of an organisation by carrying out a simulated cyber attack.
Kido's nurseries across London include central sites in Waterloo and Clerkenwell as well as locations in upmarket suburbs such as Chiswick and Fulham.
Fees vary between nurseries, but are estimated at the Chiswick site at around £2,000 a month for a child going in for a full day (8am to 6pm) for five days a week without working family funding.
The Met says its enquiries remain ongoing.