A second boy has been arrested in connection with the alleged TalkTalk cyber attack, the Metropolitan Police said.
The teenager has been bailed to a date yet to be confirmed.
A 15-year-old boy from County Antrim in Northern Ireland was arrested on Monday in connection with the alleged data theft. He was bailed until a date in November.
The investigation is being carried out by the Met’s cyber crime unit, the PSNI’s cyber crime centre and the National Crime Agency.
The latest breach is the third in a spate of cyber attacks affecting TalkTalk in the last eight months, with incidents in August and February resulting in customers’ data being taken.
Police confirmed officers also carried out a search at a residential property in Liverpool in connection with the cyber attack.
Inquiries by the Met’s cyber crime unit and officers from the National Crime Agency, the British equivalent of the FBI, continue.
The first boy arrested, from Northern Ireland, is known to like the Call Of Duty video game which simulates warfare, neighbours said.
He was described by local residents as a “quiet boy” who moved to the area recently with his family.
The arrests came after TalkTalk, the phone and broadband provider, was targeted in an alleged cyber attack a week ago.
The company said bank account numbers and sort codes may have been accessed.
But they stressed criminals would need more information to enable them to take money from a customer’s bank account, and said the chances of thieves succeeding with this was “very small indeed”.
TalkTalk chief executive Dido Harding said she was still unsure how many of the telecoms giant’s four million UK customers had been affected by the attack.