Japan’s largest mobile service provider has limited data traffic after its network faced a complete outage across the country for three hours on Thursday evening.
Some of the 80 million-strong customer base of NTT Docomo Inc. using the 3G network continued to face disruptions on Friday, Tokyo-based Kyodo News reported.
Mobile phone users are facing problems in making calls and use data connections.
The system failure was reported around 5 p.m. on Thursday (0800GMT) “due to troubles during work on its network,” the company said.
“The system responded in an unexpected way during the work. Data that had backed up during the outage overwhelmed the system when the company tried to restore services,” it said.
However, services were restored three hours later.
“But connections remained unstable for some users due to network congestion as many people tried to access the network,” said the company.
Yasushi Kaneko, Japans’ internal affairs and communications minister, asked the NTT Docomo to probe the cause of the massive service disruption “in detail and report the scope of users affected.”
“It is very regrettable that the (system) failure occurred to significantly affect the mobile phone service, important infrastructure for people’s lives,” Kaneko told reporters.
Authorities will also explore whether the system failure “falls under a serious incident stipulated in the law on telecommunications business based on the carrier’s report.”
If so, the NTT Docomo may be asked to take steps to avoid such failures in the future.