A high-ranking official at SK Chemicals has been arrested for trying to cover up evidence amid a probe into the case of deadly humidifier disinfectants. Prosecutors suspect that the company, now SK Discovery, might have hide toxicity-indicating data in an organized scheme.

The Seoul Central District Prosecutors’ Office on Thursday issued an arrest warrant for Park Cheol, managing director at vice president level, at SK Discovery.

Song Gyeong-ho, a senior judge in arrest warrants affairs, said, “His suspected crime has been called, and there was a concern for destroying evidence.” He dismissed arrest warrants for the other three executives.

The prosecution sought arrest warrants for the four executives of SK Chemicals, accusing them of trying to destroy a toxicity report of ingredients used in the product, “Humidifier Mate” since 2013.

Park formerly worked as a senior prosecutor at the Seoul Central District Prosecutors’ Office. He is now head of ethics management division at SK Discovery, which spun off as an operating company.

On Feb. 27, two former executives of Aekyung, including CEO Ko Kwang-hyun, were arrested on suspicion of spoliation of evidence. Key officials who were involved in the sales of Humidifier Mate are all under investigation now.

The fatal sterilizer, developed by SK Chemicals’ biotech business team in 1994, caused the second highest number of victims after a similar product of Oxy Reckitt Benckiser. However, SK Chemicals have been away from the police dragnet for years.

The past probe used to focus only on Oxy product’s ingredients PHMG and PGH, while it was SK Chemicals that developed ingredients called CMIT and MIT for humidifier disinfectants.

Indictments of officials associated with the development of CMIT and MIT had been suspended because the harmfulness of the ingredients had not been proven.

However, a nationwide network of victims last year pressed charges again against officials at SK Chemicals and Aekyung. Then, the Ministry of Environment submitted the result of an epidemiological study that proved the two ingredients’ toxicity to the prosecutors.

The prosecution raided SK Chemicals, Aekyung Industry, and E-Mart’s head office in January. The probe gained momentum after prosecutors found situational evidence that SK Chemicals destroyed a report indicating Humidifier Mate was harmful during the first production of the sterilizers in 1994.

SK Chemicals have been claiming that the company confirmed there was no toxicity problem at the time of the product development. During the process of changing the name of the company, the toxicity report has gone missing, it claimed.

However, when the controversy sparked over the danger of humidifier disinfectants made by Oxy in 2013, SK Chemicals intentionally deleted related data, the prosecution said. At the time, executives of the company ordered the data removal, it said.

The prosecution also suspects that SK Chemicals lied that it did not know PHMG, which SK Chemicals supplied for Oxy, was the ingredient for Oxy’s sterilizer.

According to the victims’ network, 6,309 people have applied for the government compensation, and 1,386 have died because of the use of the fatal sterilizers. Victims are still suffering from lung diseases with various symptoms.