A fire at a lithium battery factory in South Korea has claimed the lives of at least 22 people and injured eight, most of them Chinese nationals, according to local fire officials.

The fire, which has largely been extinguished, occurred at about 10:30am on Monday, local time, at the factory run by battery manufacturer Aricell in Hwaseong, south of the capital Seoul.

The blaze began after a series of battery cells exploded inside a warehouse with some 35,000 units, said Kim Jin-young, a local fire official. 

Eighteen Chinese workers and one Laotian were among the dead.

The nationality of the remaining deceased worker was not yet confirmed, Mr Kim said, citing information from company officials.

What had triggered the explosion also remains unclear, he added.

Mr Kim also said one factory worker remained out of contact and rescuers continued to search the site. 

He said that two of the eight injured were in serious conditions.

Mr Kim said the victims likely failed to escape via stairs to the ground. 

He said that authorities will investigate whether there were fire extinguishing systems at the site and if they worked.

Factory workers described an explosion in one battery cell on the second floor, followed by a series of explosions, Mr Kim said.

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

Fire and Disaster Prevention professor at Daejeon University Kim Jae-ho said the fire had probably spread too quickly for workers to escape.

"Battery materials such as nickel are easily flammable," he said. 

"So often, there is not enough time to respond, compared to a fire caused by other materials."

Lithium batteries are used in everything from laptops to electric vehicles — but can be highly explosive, with airlines, for example, imposing strict regulations on checking devices containing them.

South Korea is also one of the world's largest producers of high-end semiconductors, and the government has invested heavily in key technologies including displays and batteries.

AFP/Reuters