As many as 36 people were killed in a fire that broke out at a warehouse construction site in a city southeast of the South Korean capital Seoul on Wednesday, according to fire authorities.

Fire officials in Icheon said at a briefing that 10 people were injured in the blaze, which started around 1:30 p.m.

The officials suspect it was caused by a flammable material that was being used for insulation work in the underground level at the site.

(In this handout provided by Gyeonggi Province Fire Services, Smoke billows from a warehouse construction site on April 29, 2020 in Icheon, South Korea.)
[Photo courtesy of Gyeonggi Province Fire Services][Getty/Kyodo]

Around 80 people were at the site at the time the fire broke out, raising fears that the death toll could rise further.

"The fire seems to have spread extremely quickly, with the victims apparently having been unable to evacuate at all during the fire," a firefighter was quoted as saying.

According to Yonhap, the building was a cold storage warehouse with two basements and four stories above ground, and was scheduled to be completed at the end of June.