Telecom operator KDDI, faced the biggest mobile network failure in the history of Japan’s No.2 wireless carrier, affecting almost 40 million users nationwide on Saturday.
In a statement issued at 9:00 a.m. local time (0000 GMT) on Monday KDDI said data transmission had been broadly restored, but users might still experience difficulty in making voice calls due to service restrictions.
The disruption, which began in the early hours of Saturday morning, was caused by an equipment malfunction and affected services ranging from weather data to parcel delivery and banking, media reports said.
“We deeply regret this as a telecommunications carrier in a position to support critical infrastructure and provide stable services,” KDDI President Makoto Takahashi told a news conference on Sunday. He said it was the biggest system failure in the carrier’s history.
Up to 39.15 million users, including 260,000 corporate customers, have been affected by the glitch, which was triggered by a malfunction in equipment for providing voice call services, the company said, adding the detailed causes were still being investigated.
The widespread network errors have disrupted transmission of weather data at the Meteorological Agency, automated teller machines at Ogaki Kyoritsu Bank, a regional bank in central Japan and the communication system for the parcel delivery at Yamato Holdings, according to their websites.
Toyota Motor, Mazda Motor and Subaru also had problems with some functions in their internet-connected vehicle services, the Nikkei business daily said.
Japan’s government will take necessary measures after receiving an official report from KDDI, Yasushi Kaneko, minister for internal affairs and communications, said on Sunday.
KDDI customers flooded Twitter to complain, with one claiming some taxi drivers were not able to take credit cards or electronic payment because of the outage.
“We take this issue very seriously and expect KDDI to explain in detail what happened to those who were affected,” Deputy Chief Cabinet Secretary Seiji Kihara told reporters on Monday.
“Many couldn’t use mobile phone service – important infrastructure for daily life and the global economy – for a long time, and we find that very disappointing,” the government spokesperson said.
“The main risk is that more outages are possible because network complexity is difficult to manage,” said Redex Research analyst Kirk Boodry, who publishes on the Smartkarma platform.
Japan’s three big telcos have all had widespread network failures in recent years.
NTT Docomo’s outage last October affected 12.9 customers, while disruption to SoftBank’s network in late 2018 cast a shadow over its bumper public listing.