Trains stacked up in cascading delays, with some stations near entry restrictions. Taiwan's Liberty Times covered the scene — 'stations about to overflow.'

KORAIL and Seoul Metro inspected power systems and restored service in stages; the cause is under investigation.

Commuters flooded buses and taxis, snarling street traffic, while tardy-slip selfies and platform photos swamped social media.

Line 1, the network's oldest, has long faced aging-equipment concerns; experts urge planned replacement of power and signal systems.

With heatwave power demand surging, calls are growing for a summer power-management review across urban rail.