Hong Kong's communications watchdog has told telecoms operator SmarTone to submit a report after an outage yesterday left many of its subscribers disconnected. The Sun Hung Kai Properties subsidiary blamed the issue on a server fault plaguing its systems that caused a 20-minute breakdown of voice and data services on its 3G and 4G networks around lunchtime. The issue is believed to have affected tens of thousands of SmarTone's 1.9 million customers. When the network went down, users in Causeway Bay, Tsim Sha Tsui, Mid-Levels, Pok Fu Lam, North Point, Taikoo and Admiralty resorted to Wi-fi and social media to bombard the company with complaints and more went in-store to overcome the mobile blackout. Anybody using Smartone in CWB? Is it the network is down or is it just me? — Johnathan Lam (@Millennium14) February 12, 2015 Reports from as far away as Science Park that no Smartone service working in Hong Kong. — PenguinSix (@PenguinSix) February 12, 2015 An Office for the Communications Authority (Ofca) spokeswoman said SmarTone reported the issue at 1pm. As of 5pm, the watchdog had received 17 inquiries and complaints. "OFCA has requested SmarTone submit a preliminary report on the incident in three working days," Ofca said. Ken To, a company spokesman, said the service disruption started at noon and lasted 20 minutes. But some customers reported that they experienced problems for more than four hours. "One of the servers responsible for users' connection to the network encountered [a] malfunction. Voice and Data services for certain customers might be intermittently unavailable … We apologise for any inconvenience caused," said To. Jason Oke, an advertising agency executive in Quarry Bay, complained he lost service for more than four hours. "Wow, the whole SmarTone cell network seems to have been down for the past half hour. Well done," he said, earlier in the outage. And Taikoo-based Tung Ng, an investment adviser, expressed frustration at the outage but also relief that the network issue was not related to his own handset.