The massive fire at a lithium battery factory in Hwaseong, Gyeonggi Province, on Monday has shed light on the irregularities in the hiring system for workers of foreign nationality here, with local employers suspected of abusing loopholes in the labor law for their benefit, to cut costs while avoiding responsibility.

Local battery manufacturer Aricell, the operator of the plant, where the deadly fire killed 23 people, among which 18 were foreign national workers, was later found not to be even authorized to hire them.

Of the victims, most of them were F-4 overseas Korean visa holders, with the rest on the H-2 work and visit visa, F-6 spouse of a Korean national visa and F-5 permanent residency visa, according to local reports.

For Korean businesses to hire a foreign worker with an H-2 visa, they must be a small or medium-sized manufacturer with fewer than 300 workers and market capital of not more than 8 billion won ($5.8 million), according to current law. If they seek to hire workers of foreign nationality despite failing to meet both these two criteria, then they must receive a “Certificate of Small & Medium Enterprise Confirmation” from the regional Small & Medium Enterprise Administration.

Aricell's total market cap, however, stood at 25 billion won as of the end of last year, according to data provided by the state-run watchdog Financial Supervisory Service. On top of that, an official at the Ministry of Employment Labor, who requested anonymity, recently confirmed that Aricell did not hold the aforementioned required certificate from the regional SME Administration.

On Tuesday, Aricell CEO Park Soon-kwan, who is also the chief of Aricell’s parent company, S-connect, denied accusations of illegally employing foreign workers, claiming most of his company's labor force consists of subcontracted day laborers dispatched by a human resources agency.

Park also claimed that it was the human resources agency that gave instructions to the workers, in an apparent move to dodge blame about not having provided the workers with proper safety-related job training.

However, experts raised questions about the share of foreign workers in Aricell's labor force, which according to Park accounted for half the staff. Of the total 103 employees working at Aricell, more than half -- 53 -- were workers of foreign nationality.

"The ratio of foreign workers at Aricell shows that it's a company that depends heavily on foreign workers," said Kim Sung-hee, a professor at Korea University Graduate School of Labor Studies via phone.

"It is highly suspected that this is a case of illegal hiring of foreign workers aimed at gaining cheap labor without appropriate safety measures," he said.

Labor Ministry data acquired and released by a ruling party lawmaker on Tuesday showed that the number of foreign workers who were reported to have died in industrial accidents came to 85 last year, accounting for 10.4 percent of the total death toll.