Samsung Electronics Co. is partly responsible for last week's highly poisonous hydrofluoric acid leak at its main chip plant in southwestern South Korea, a government official said Tuesday.

For the second time in just three months, a small amount of diluted hydrofluoric acid, a colorless acute poison that can damage the lungs and bones and even affect the nervous system, leaked at the semiconductor plant in Hwaseong, 60 kilometers south of Seoul, on Thursday, injuring three subcontract workers.

After looking into the cause of the leak, the Ministry of Labor and Employment tentatively concluded that Samsung Electronics is also liable for the incident as it was the contractor, according to the high-ranking ministry official.

Three workers from Seongdo ENG -- Samsung's subcontractor -- burned their hands as they were upgrading parts of an existing facility that contained hydrofluoric acid residue.

"The contractor (Samsung Electronics) should hold responsibility in securing safety as it was not an outside subcontracting work but an in-house subcontracting work," the official said, adding that a supervisor from Samsung was at the site.

According to the ministry, the world's top chipmaker has denied its responsibility saying another subcontractor, the STI Service, had not completely removed the hydrofluoric acid that was left in the pipes.

The ministry will soon notify state prosecutors of the opinion that Samsung Electronics holds partial responsibility, the official added.

The apparent accident is the second of its kind reported by the world's top chipmaker so far this year.

On Jan. 28, up to 10 liters of diluted hydrofluoric acid leaked from the same Samsung factory, killing one worker and injuring four others.

The ministry said it is continuing a separate probe with the prosecutors into the January incident, after judging that Samsung is partially responsible. (Yonhap News)