Electronics giant recruits specialist to track down hackers who stole personal details of more than 100 million online gamers Sony has hired private investigators to track down the computer hackers who stole the personal details of more than 100 million online gamers.

Meanwhile the UK information commissioner's office, which probes data breaches of this kind, said on Wednesday that it has contacted Sony and is making inquiries into whether to investigate the attack, which affected a number of UK gamers.

The Japanese electronics giant has recruited a former special agent with the US Naval Investigative Service to work alongside security experts from Guidance Software and Protiviti in the aftermath of the online attack. The FBI has launched a separate investigation into the huge breach.

Although investigators are not thought to be close to identifying the culprits, at least some of the attacks came from a Malaysia-based server, according to the Wall Street Journal. It is not clear whether attacks were launched from the south-east Asian country or whether only the server was used.

The crisis at Sony deepened on Tuesday after the company admitted that the names, email addresses, phone numbers of 25m Sony Online Entertainment (SOE) customers were stolen in the attack, which also hit 77m PlayStation Network (PSN) gamers. Debit card records of 10,700 customers in Austria, Germany, the Netherlands and Spain were compromised in the attack, Sony said.

Sony moved to placate growing fears over the security of its users after earlier declining a chance to testify in front of a US congressional hearing. A spokeswoman for the company admitted that an "outdated database" from 2007, featuring personal details belonging to 23,400 people outside the US, was broken into on 16 and 17 April – two days prior to the huge PSN attack. A Canadian law firm on Tuesday launched a $1bn (£600m) proposed class action lawsuit against Sony for breach of privacy.

The company admitted that it did not known when or where the next attack would come. "They are hackers. We don't know where they're going to attack next," the spokeswoman said. Another Sony spokeswoman said that there was no evidence that the stolen personal details had yet been used for financial gain. However, some people have contacted the Guardian saying that they have seen unusual activity on their account: one said that since the attack they had seen money regularly taken from their account via a cash machine in Florida.

Connecticut senator Richard Blumenthal wrote to Sony on Tuesday asking how many credit card accounts were compromised in the attack, which first came to light last week. Blumenthal said he would ask US attorney general Eric Holder to investigate whether the company's handling of the breach makes it civilly or criminally liable to prosecution.

The PlayStation Network remains offline after being shut down more than two weeks ago, when Sony first discovered the breach.