Fire trucks arrive at the scene of a fire at a battery manufacturing factory in Hwaseong, Gyeonggi Province on Monday. (Gyeonggi Fire and Disaster Headquarters)

At least 16 people have been confirmed dead in Monday's battery factory fire in Hwaseong as of 5 p.m., with the final death toll expected to rise above 20.

Of the 23 people who had earlier been reported missing in the fire, 20 were confirmed to be foreign nationals.

The rescue authorities commenced a search of the lithium primary battery plant, run by Aricell, after firefighters got the blaze under control at 3:10 p.m. It was over three hours after the fire first broke out on the second floor of the three-story factory building at 10:31 a.m.

Earlier in the day, Gyeonggi Fire and Disaster Headquarters had confirmed the death of a factory worker in his 60s of South Korean nationality, who had managed to escape the building but sustained fatal injuries in the fire. At least six people were reported to have been injured in the fire in Seosin-myeon of the southern Gyeonggi Province city, some 62 kilometers south of Seoul.

An unspecified cause led to the fire in the plant that had at least 35,000 lithium batteries inside, many of which caused subsequent explosions that made it difficult for firefighters to extinguish the fire.

Minister of Interior and Safety Lee Sang-min visited the site after earlier in the day stressing cooperation between the related agencies and the regional governments to ensure that no additional lives are lost in the fire while ordering "all available firefighting personnel and equipment to do everything possible to extinguish the fire and rescue survivors."

A level 2 emergency response was issued by the Gyeonggi Fire and Disaster Headquarters. A level 1 response is issued in situations thought to be manageable by a fire station that has jurisdiction in the area of a disaster, while level two is issued for situations that require the responses of multiple fire stations in the vicinity.