Aug 27 (Reuters) - T-Mobile US Inc (TMUS.O) said on Friday it was confident there were no continuing risks to user data from a breach disclosed earlier this month that affected more than 53 million current, former and prospective customers. The third largest U.S. wireless carrier last week said personal data of more than 40 million former and prospective customers was stolen along with data from 7.8 million existing customers. read more In another update, which came days after the U.S. Federal Communications Commission opened a probe into the breach, T-mobile revealed that 5.3 million additional wireless subscribers and 667,000 more accounts of former customers were impacted, bringing the total to more than 53 million. read more "We recognize that many are asking exactly what happened. While we are actively coordinating with law enforcement on a criminal investigation, we are unable to disclose too many details," Chief Executive Officer Mike Sievert said in a blog post on Friday. The wireless carrier in a filing also said it had partnered with experts at cybersecurity firm Mandiant and consulting firm KPMG following the hack. (https://bit.ly/3ztRaQQ) John Binns, a 21-year-old hacker who stole data of T-Mobile customers, said the company"s security was "awful", the Wall Street Journal reported on Thursday. read more