A fire erupted at a POSCO plant Friday evening after what appears to be a series of explosions at a blast furnace, witnesses and authorities said. No casualties were reported.

Firefighters said the flames were brought under control in an hour.

Witnesses reported seeing a big flame rising over the plant with what sounded like four to five explosions at around 8:50 p.m.

Some said they felt the ground shake. A number of homes nearby reported broken windows.

Company officials said high-temperature slag, a by-product from when metals are extracted from their ores, seems to have reacted when it combined with a pool of rainwater. (Yonhap News)