A massive blackout reportedly hit Taiwan on Thursday in two of its biggest cities during former U.S. Secretary of State Mike Pompeo’s visit.

“Taiwan reported a massive blackout on Thursday that is affecting its two biggest cities as well as its most important iPhone processor production hub,” reported Nikkei Asia. “Government officials estimate about 5 million households are affected by the power outages, including in Taipei, the capital, and Kaohsiung, the second-biggest city.”

Though details remain scant at the moment, Taiwan Power Co. said in a brief statement that the massive blackout was sparked by a malfunction in the southern power grid system at the Kaohsiung’s Hsinta Power Plant, with knock-on effects contributing to power outages in northern and central Taiwan as well. President Tsai Ing-Wen apologized for the outage.

“Economic Minister Wang Mei-Hua said a government team is doing its best to restore power to northern Taiwan by noon,” said the report. “To deal with the malfunction, Hsinta Power Plant must be cut off from other power plants, she said, explaining that it will then take time to restore and restart those plants.”

“Tainan Science Park — the site of TSMC’s most cutting-edge chip production plants for iPhone processors — reported sudden and abnormal voltage changes to the site’s power supply but said it is still determining whether those changes have had any impact on the park,” it added.

Tainan Science Park hosts tech plants for TSMC, United Microelectronics and Foxconn display affiliate Innolux.

The power outage ironically occurred during the visit of former U.S. Secretary of State Mike Pompeo, who will meet with President Tsai on Thursday. However, despite the coincidence and the high security threat from China at this time, reports indicate the outage was not the result of hacking.

Taiwan has suffered massive power outages before, one in 2021, which affected four million households and one in 2017, which affected 6.68 million households.