At least one person has been killed, four others injured and 23 missing after a fire broke out at a lithium battery production plant in Hwaseong, Gyeonggi Province.

According to fire authorities, a man in his sixties died from cardiac arrest after the fire broke out at around 10:30 a.m. on Monday.

While firefighters continue efforts to put out the flames, authorities are focused on searching for victims still in the plant.

An estimated total of 67 people were said to be working inside the factory at the time of the fire. Twenty of the 23 people still unaccounted for are foreigners, two are Korean while the nationality of one person is unknown. 

The cause of the fire at the three-story concrete steel building is currently unknown. 

Authorities proactively issued a Level Two alert requiring up to seven fire stations to mobilize a maximum 50 units of fire fighting equipment.

The Hwaseong city government, meanwhile, sent out disaster alert texts to local residents, urging them to refrain from outdoor activities due to the possible release of toxic substances from the fire.