Police have recently made a second arrest, that of a 16-year-old boy from west London, in connection with the investigation into the alleged theft of data from TalkTalk.
He was arrested on suspicion of offences including computer misuse after detectives searched a Feltham address, and was later bailed, Scotland Yard said.
On Monday, another boy, 15 years old this time, was arrested and bailed in Northern Ireland in connection with the hacking.
The TalkTalk website was hit by a "significant" cyber-attack last week.
The phone and broadband provider, which has more than four million customers in Britain, said that both banking details and personal information on the TalkTalk website could have been compromised by hackers.
Officers are still searching the address of the Liverpool residence, the Metropolitan Police said in a statement.
News of the hacking first broke last Wednesday, with telecoms TalkTalk publicly warning its customers that their details could be used against their will by fraudsters.
CEO Dido Harding later said that the scale of the attack was ultimately “smaller” than initially believed, and that any credit card details compromised would have been incomplete.
MPs are set to launch an inquiry into the cyberattack, with Culture Minister Ed Vaizey arguing that the government is not against encryption when it comes to businesses holding customer data.
