Firefighters say they have managed to put out most of the massive blaze that broke out at a Coupang distribution center in Gyeonggi Province.

Authorities revealed Friday afternoon they were using water cannons to put out the remaining flames from outside the building instead of from within, amid concern the structure may soon collapse.

The fire began in the basement of the e-commerce giant's four-story warehouse in Icheon after 5 a.m. on Thursday.

It appeared to have been caused by a spark from a power outlet.

An investigation into the cause is still ongoing.

According to officials, all employees on site were evacuated, but one firefighter is believed to be trapped inside after he entered the basement to look for people left behind.