Millions of South Koreans were left without power Thursday after unseasonable temperatures pushed up demand while many of the country's power plants were shut down for maintenance.

The Ministry of Knowledge Economy said officials were surprised by the hot weather, which caused increased use of cooling systems. Temperatures in many parts of South Korea rose above 30 degrees Celsius.

Power outages were reported around Seoul, including the Yeouido financial district, and hundreds of thousands of homes were affected. Cell phone service was disrupted, traffic signals were inoperable and many factories were shut down.

Police said they received thousands of calls from people trapped in elevators.