SEOUL, June 25, 2024 (BSS/AFP) - South Korean investigators combed the charred wreckage of a lithium factory Tuesday to find the cause of a massive blaze that killed 23 in one of the country's worst factory disasters in years.

The fire department said 23 people are now confirmed dead, including 17 Chinese nationals -- one fewer than their initial figure of 18, with identification work ongoing.

"We plan to confirm the victims' identities by collecting DNA from their bodies," firefighter Kim Jin-young told reporters.

The government launched its formal investigation on Tuesday, involving ministries and departments from across the board, to pinpoint the exact cause of the fire, with investigators entering the building.

Over 100 people were working in the factory when workers heard a series of explosions from the second floor, where lithium-ion batteries were being inspected and packaged.

CCTV footage from the entrance of the factory building shows white smoke filling the area in less than 20 seconds, as people race out, the Yonhap news agency reported.

Toxic fumes likely quickly overwhelmed workers in the area where the blaze began, the fire department has said, adding that as it was a lithium fire, the workers' efforts to extinguish wouldn't have worked.

Park Soon-kwan, CEO of Aricell, the owner of the lithium battery plant, apologised on Tuesday for the fire, saying the company would "support the needs in every way" of the families of the victims.

He said the company would cooperate with investigators, adding that it had had dry-powder fire extinguishers throughout the building, and conducted regular safety training drills for employees.

Xing Haiming, Chinese Ambassador to Seoul, visited the site of the fire late Monday, calling it an "unfortunate and heartbreaking," incident, but saying he "had a good conversation with the Korean government" on preventing any reoccurrence.

"It is hoped that South Korean businesses will learn a painful lesson, refrain from similar incidents in the future and earnestly safeguard the safety of Chinese citizens in South Korea," he said.

South Korea's President Yoon Suk Yeol also visited the disaster site late Monday, and ordered authorities to check similar factories that handle chemicals and take "measures to prevent such accidents from happening again."

Lithium batteries burn hot and fast, and are difficult to control with conventional fire extinguishing methods.

South Korea is a major producer of batteries, including those used in electric vehicles.