Steelmaker Posco said Tuesday it reactivated five furnaces that were shut down at its Gwangyang steel mill due to a blackout the day before.

On Monday, the company halted the operation of five furnaces at its steel mill due to a power failure.

Posco said all the five furnaces have returned to normal operations and all other major production facilities are running as usual. 

The blackout is estimated to temporarily increase fixed costs by at least 40 billion won ($34 million) due to reduced production of around 50,000 tons. However, Posco added, it expects those losses to be offset this year by additional production.

Posco said the blackout occurred in the process of fixing circuit breakers of a substation. The power failure led to the suspension of a ventilator that put hot wind in furnaces, which was halted consequently. For less than an hour, black smoke billowed from the mill. But there were no fires, explosions or casualties.

By Shin Ji-hye (shinjh@heraldcorp.com)