At least 22 workers were killed when multiple lithium-ion batteries exploded in a South Korean battery factory Monday morning, sparking a ferocious fire that spewed highly toxic gas as flames tore through the plant.

The batteries that blew up around 10:30 a.m. were being stored in a warehouse that held 35,000 cells in the industrial city of Hwaesong, about 25 miles south of Seoul, according to Reuters.

The fire spread within 15 seconds and the victims likely died after just one or two breaths, said Gyeonggi province fire official Cho Sun-ho.

Aerial video reportedly showed explosions rolling through the factory and massive plumes of white smoke coming from the ruins.

Live TV coverage also showed firefighters spraying water on the building, large chunks of which appeared to have been blown out into the street, Reuters said.

Parts of the upper level also collapsed.

It took about six hours for firefighters to bring the blaze under control.

The intensity of the fire made it hard for rescuers to identify the dead, who included 18 Chinese nationals, two South Koreans and a Laotian, Hwaseong fire official Kim Jin-young told reporters, citing factory owner Aricell.

The company's website was down and Reuters said calls to its offices went unanswered.

Most of the foreign workers were temporary hires who were probably unfamiliar with the factory's layout, the provincial fire official said.

South Korean President Yoon Suk Yeol visited the scene and Interior Minister Lee Sang-min called on local authorities to prevent any hazardous chemicals from contaminating the surrounding area.