Hydrofluoric acid was discharged from a Samsung Electronics chip plant in Hwaseong, Gyeonggi, where one worker died and four others were injured in an acid leak in January.

According to the company, three workers from Sungdo Engineering and Construction who were dismantling gas pipes in a Central Chemical Supply System (CCSS) were exposed to the hydrofluoric acid, a colorless poison that can damage the lungs, bones and nervous system, around 11:30 a.m. yesterday.

The workers, identified by the surnames Choi, 45, Song, 40, and Lee, 28, were immediately sent to Ajou University Hospital.

Samsung said in a press release that the workers were not seriously injured because they were wearing protection including acid-proof gloves, goggles and protective masks.

Samsung told reporters the workers were replacing a hydrofluoric acid tank that the Ministry of Employment and Labor ordered to be removed after the January gas leak. It said gas splashed on the workers when they cut the pipes.

On Jan. 28, up to 10 liters (2.64 gallons) of diluted hydrofluoric acid leaked from a pipe at the main semiconductor plant, killing one worker and injuring four others in eight hours.

After the January leak, the Labor Ministry conducted an inspection of the Hwaseong plant and announced they found a total of 1,934 violations in the managing of the facility. Last month, the Gyeonggi Provincial Police Agency charged three officials of Samsung with dereliction of duty.

“We have secured CCTV footage of the scene to check whether the workers violated any safety rules,” a spokesman of the police said. “We will inspect the plant with officials from the Labor Ministry and the Ministry of Environment to find out the exact causes of the accident.” The Environment Ministry said it measured the atmosphere but toxic gas wasn’t detected.

By Choi Mo-ran [sakwon80@joongang.co.kr]